[ { "id": "MV501-001", "module": "MV-501", "level": "B", "region": "All", "question": "What voltage range is usually called medium voltage in distribution?", "options": [ "132 kV to 400 kV", "Below 1 kV", "Above 1 kV up to about 36 kV", "Above 500 kV" ], "answer": 2, "explanation": "MV normally covers 6.6, 11, 13.8, 22 and 33 kV systems.", "ref": "IEC 60038" }, { "id": "MV501-002", "module": "MV-501", "level": "B", "region": "All", "question": "Why is electricity transmitted at high voltage?", "options": [ "It is safer to touch", "Cables are cheaper", "Transformers need it", "Lower current means much lower I²R losses" ], "answer": 3, "explanation": "For the same power, doubling the voltage halves the current and quarters the losses.", "ref": "" }, { "id": "MV501-003", "module": "MV-501", "level": "B", "region": "GCC", "question": "What is the main MV distribution voltage in Dubai?", "options": [ "11 kV", "33 kV", "6.6 kV", "22 kV" ], "answer": 0, "explanation": "DEWA distributes at 11 kV from 132/11 kV substations.", "ref": "" }, { "id": "MV501-004", "module": "MV-501", "level": "B", "region": "KSA", "question": "Which GCC country runs its grid at 60 Hz?", "options": [ "UAE", "Qatar", "Saudi Arabia", "Oman" ], "answer": 2, "explanation": "Saudi Arabia is 60 Hz. The other GCC states are 50 Hz.", "ref": "" }, { "id": "MV501-005", "module": "MV-501", "level": "B", "region": "KSA", "question": "Which MV distribution voltage is common in Saudi cities?", "options": [ "13.8 kV", "22 kV", "11 kV", "66 kV" ], "answer": 0, "explanation": "SEC uses 13.8 kV widely, with 33 kV also in use.", "ref": "" }, { "id": "MV501-006", "module": "MV-501", "level": "B", "region": "AU", "question": "Which distribution voltages are most common in Australia?", "options": [ "6.6 and 13.8 kV", "33 and 66 kV", "11 and 22 kV", "400 V only" ], "answer": 2, "explanation": "11 kV and 22 kV are the main distribution voltages, with 33 and 66 kV for subtransmission.", "ref": "" }, { "id": "MV501-007", "module": "MV-501", "level": "B", "region": "NZ", "question": "Who operates the national transmission grid in New Zealand?", "options": [ "Vector", "EECA", "Orion", "Transpower" ], "answer": 3, "explanation": "Transpower runs the 220 kV and 110 kV grid, including the HVDC link.", "ref": "" }, { "id": "MV501-008", "module": "MV-501", "level": "B", "region": "Asia", "question": "What is the main distribution voltage in Singapore?", "options": [ "11 kV", "22 kV", "66 kV", "33 kV" ], "answer": 1, "explanation": "SP Group distributes mainly at 22 kV, with 6.6 kV in some areas.", "ref": "" }, { "id": "MV501-009", "module": "MV-501", "level": "B", "region": "All", "question": "What is the LV supply voltage at most buildings in the GCC, AU, NZ and much of Asia?", "options": [ "690 V", "110/220 V", "400/230 V", "480/277 V" ], "answer": 2, "explanation": "400 V three-phase, 230 V single-phase is the IEC standard voltage.", "ref": "IEC 60038" }, { "id": "MV501-010", "module": "MV-501", "level": "B", "region": "All", "question": "What equipment steps 11 kV down to 400 V at a building?", "options": [ "A distribution transformer", "A generator", "A capacitor bank", "A busduct" ], "answer": 0, "explanation": "The distribution transformer in the substation does the final step-down.", "ref": "" }, { "id": "MV501-011", "module": "MV-501", "level": "B", "region": "All", "question": "What does a normally open point (NOP) do in an MV ring?", "options": [ "Limits fault current", "Splits the ring so each half is fed from one end", "Measures energy", "Earths the ring" ], "answer": 1, "explanation": "Rings are built as loops but run open at one point.", "ref": "" }, { "id": "MV501-012", "module": "MV-501", "level": "B", "region": "All", "question": "In an open ring, what happens after a cable fault once switching is complete?", "options": [ "All substations are back on supply", "Only the primary is on", "Half the ring stays off until repair", "The whole city is off" ], "answer": 0, "explanation": "The faulted section is isolated and the NOP closed to back-feed.", "ref": "" }, { "id": "MV501-013", "module": "MV-501", "level": "B", "region": "All", "question": "Which network design leaves customers beyond a cable fault off until the repair?", "options": [ "Open ring", "Mesh with automation", "Closed ring", "Radial" ], "answer": 3, "explanation": "Radial feeders have only one supply path.", "ref": "" }, { "id": "MV501-014", "module": "MV-501", "level": "B", "region": "All", "question": "What does FLISR stand for?", "options": [ "Fault Location, Isolation and Service Restoration", "Fast Line Insulation Switching Relay", "Feeder Load Isolation Safety Rule", "Fault Level Indicator Switching Regime" ], "answer": 0, "explanation": "Automated restoration using remote switches, FPIs and SCADA.", "ref": "" }, { "id": "MV501-015", "module": "MV-501", "level": "B", "region": "All", "question": "What does a fault passage indicator show?", "options": [ "Energy use", "Voltage level", "Whether fault current has passed through that point", "Phase rotation" ], "answer": 2, "explanation": "Crews follow the flagged FPIs to the faulted section.", "ref": "" }, { "id": "MV501-016", "module": "MV-501", "level": "P", "region": "All", "question": "What does a closed ring need at every substation to avoid outages for a single cable fault?", "options": [ "Load break switches only", "Fuses", "Surge arresters", "Circuit breakers with unit protection" ], "answer": 3, "explanation": "Only the faulted section is tripped, using differential or pilot wire protection.", "ref": "" }, { "id": "MV501-017", "module": "MV-501", "level": "P", "region": "All", "question": "Why are open rings preferred over closed rings in most cities?", "options": [ "They carry more load", "They avoid earthing", "They have no outages", "They need only simple protection and low-cost switches" ], "answer": 3, "explanation": "Closed rings need breakers and unit protection everywhere, which costs much more.", "ref": "" }, { "id": "MV501-018", "module": "MV-501", "level": "P", "region": "All", "question": "What usually holds the 11 kV busbar voltage constant at a primary substation?", "options": [ "On-load tap changers on the power transformers", "Off-circuit taps", "Capacitor banks only", "The RMU" ], "answer": 0, "explanation": "OLTCs regulate the MV bus voltage as load changes.", "ref": "" }, { "id": "MV501-019", "module": "MV-501", "level": "P", "region": "All", "question": "Which reliability index measures average outage minutes per customer per year?", "options": [ "SAIDI", "MAIFI", "CAIDI", "SAIFI" ], "answer": 0, "explanation": "SAIDI is System Average Interruption Duration Index.", "ref": "" }, { "id": "MV501-020", "module": "MV-501", "level": "P", "region": "All", "question": "Automating open rings with FLISR mainly reduces which index?", "options": [ "Frequency", "Power factor", "SAIDI", "Fault level" ], "answer": 2, "explanation": "Faster restoration cuts the minutes off supply.", "ref": "" }, { "id": "MV501-021", "module": "MV-501", "level": "B", "region": "All", "question": "Which neutral earthing method gives the highest earth fault current?", "options": [ "Resonant", "Solid", "High resistance", "Isolated" ], "answer": 1, "explanation": "Solid earthing allows fault current near the three-phase level.", "ref": "" }, { "id": "MV501-022", "module": "MV-501", "level": "B", "region": "All", "question": "What limits earth fault current on a resistance earthed system?", "options": [ "The LV load", "The cable length", "The neutral earthing resistor", "The transformer kVA" ], "answer": 2, "explanation": "The NER is sized for a set earth fault current.", "ref": "" }, { "id": "MV501-023", "module": "MV-501", "level": "P", "region": "All", "question": "On an isolated or resonant earthed system, the healthy phases during an earth fault rise to about...", "options": [ "3 pu always", "0 pu", "1.0 pu", "1.73 pu (line voltage to earth)" ], "answer": 3, "explanation": "With the faulted phase at earth potential, the others sit at line voltage to earth.", "ref": "" }, { "id": "MV501-024", "module": "MV-501", "level": "P", "region": "All", "question": "What does a Petersen coil do?", "options": [ "Measures energy", "Limits overload", "Cancels the cable capacitive earth fault current", "Filters harmonics" ], "answer": 2, "explanation": "It is tuned to the network capacitance so arcs self-extinguish.", "ref": "" }, { "id": "MV501-025", "module": "MV-501", "level": "P", "region": "AU", "question": "Why does Victoria require REFCLs in some zone substations?", "options": [ "To reduce losses", "For harmonics", "To cut the chance of earth faults starting bushfires", "For metering" ], "answer": 2, "explanation": "REFCLs reduce fault energy almost to zero within milliseconds.", "ref": "" }, { "id": "MV501-026", "module": "MV-501", "level": "P", "region": "All", "question": "What mainly sets the capacitive charging current of an MV network?", "options": [ "Total cable length and capacitance", "LV load", "Transformer size", "Relay settings" ], "answer": 0, "explanation": "Ic = 3ωC·U0 per phase, summed over all cable length.", "ref": "" }, { "id": "MV501-027", "module": "MV-501", "level": "P", "region": "All", "question": "For an 11 kV system, what is the phase-to-earth voltage U0?", "options": [ "6.35 kV", "11 kV", "19 kV", "3.8 kV" ], "answer": 0, "explanation": "U0 = 11 / √3 = 6.35 kV.", "ref": "" }, { "id": "MV501-028", "module": "MV-501", "level": "P", "region": "All", "question": "What is a typical reason to use high resistance earthing?", "options": [ "To avoid insulation", "To raise fault current", "To allow continued operation during a single earth fault", "To trip fast" ], "answer": 2, "explanation": "Common in process plants that cannot stop on the first earth fault.", "ref": "" }, { "id": "MV501-029", "module": "MV-501", "level": "E", "region": "All", "question": "Which risk increases with an isolated neutral during intermittent earth faults?", "options": [ "Low fault current", "Frequency drift", "Arcing overvoltages of 2.5 to 3 pu", "Lower voltage" ], "answer": 2, "explanation": "Restriking arcs can pump up the voltage on healthy phases.", "ref": "" }, { "id": "MV501-030", "module": "MV-501", "level": "E", "region": "All", "question": "In an open ring, closing the NOP briefly parallels two feeders. What must be checked first?", "options": [ "Nothing", "The LV tap", "Only the weather", "That both feeders are from the same source or in phase and protection can accept it" ], "answer": 3, "explanation": "Paralleling feeders from different sources can cause large circulating currents.", "ref": "" }, { "id": "MV501-031", "module": "MV-501", "level": "B", "region": "GCC", "question": "What transmission voltage links the GCC national grids?", "options": [ "132 kV", "765 kV", "220 kV", "400 kV" ], "answer": 3, "explanation": "The GCC Interconnection operates at 400 kV.", "ref": "" }, { "id": "MV501-032", "module": "MV-501", "level": "B", "region": "Asia", "question": "Which transmission voltage is used in India's backbone grid?", "options": [ "11 kV", "132 kV only", "66 kV", "765 kV and 400 kV" ], "answer": 3, "explanation": "India uses 765 kV and 400 kV for bulk transmission.", "ref": "" }, { "id": "MV501-033", "module": "MV-501", "level": "P", "region": "AU", "question": "What are SWER lines used for in Australia?", "options": [ "Rural single wire earth return supply", "Data centres", "Substations", "City networks" ], "answer": 0, "explanation": "SWER supplies sparse rural loads at low cost.", "ref": "" }, { "id": "MV501-034", "module": "MV-501", "level": "B", "region": "All", "question": "What does a primary or zone substation do?", "options": [ "Meters customers", "Generates power", "Steps transmission or subtransmission voltage down to MV and splits it into feeders", "Stores energy" ], "answer": 2, "explanation": "It feeds the MV distribution network.", "ref": "" }, { "id": "MV501-035", "module": "MV-501", "level": "B", "region": "All", "question": "Where is power usually generated?", "options": [ "At around 11 to 24 kV", "At 400 V", "At 400 kV", "At 11 V" ], "answer": 0, "explanation": "Generators produce 11 to 24 kV, then step-up transformers raise it.", "ref": "" }, { "id": "MV501-036", "module": "MV-501", "level": "P", "region": "All", "question": "What vector group is common for generator step-up transformers?", "options": [ "Dzn0", "Dyn11", "YNd11 (or YNd1)", "Yyn0" ], "answer": 2, "explanation": "Delta on the generator side, earthed star on the HV side.", "ref": "" }, { "id": "MV501-037", "module": "MV-501", "level": "P", "region": "All", "question": "What protection usually trips an 11 kV underground feeder at the primary substation?", "options": [ "Buchholz", "RCDs", "Overcurrent and earth fault relays on the feeder CB", "Fuses" ], "answer": 2, "explanation": "Feeder CBs have 50/51 and 50N/51N protection.", "ref": "" }, { "id": "MV501-038", "module": "MV-501", "level": "P", "region": "All", "question": "Why is auto-reclose usually not used on all-underground cable feeders?", "options": [ "It is illegal", "Cable faults are almost always permanent, so reclosing adds damage", "Cables cannot be tripped", "It is too slow" ], "answer": 1, "explanation": "Auto-reclose suits transient overhead line faults.", "ref": "" }, { "id": "MV501-039", "module": "MV-501", "level": "E", "region": "All", "question": "A 40 km cable network at 11 kV with 0.4 µF/km per phase has a charging current of roughly...", "options": [ "96 A", "1 kA", "500 A", "10 A" ], "answer": 0, "explanation": "3 × 2π × 50 × 0.4e-6 × 40 × 6351 ≈ 96 A.", "ref": "" }, { "id": "MV501-040", "module": "MV-501", "level": "E", "region": "All", "question": "Which earth fault relay principle suits resonant earthed networks?", "options": [ "Directional, transient or admittance earth fault", "Frequency", "Undervoltage", "Simple overcurrent" ], "answer": 0, "explanation": "Fault currents are tiny, so special principles are needed.", "ref": "" }, { "id": "MV501-041", "module": "MV-501", "level": "B", "region": "All", "question": "What does SCADA let a control centre do?", "options": [ "Test relays", "Monitor and remotely control network equipment", "Generate power", "Build cables" ], "answer": 1, "explanation": "Supervisory Control And Data Acquisition.", "ref": "" }, { "id": "MV501-042", "module": "MV-501", "level": "P", "region": "NZ", "question": "Which MV voltages do NZ lines companies commonly use for distribution?", "options": [ "400 V", "11 and 22 kV", "6.6 and 13.8 kV", "66 and 132 kV" ], "answer": 1, "explanation": "11 kV is common, with 22 kV in some networks.", "ref": "" }, { "id": "MV501-043", "module": "MV-501", "level": "P", "region": "GCC", "question": "In the UAE, what are typical primary substation ratios?", "options": [ "11/0.4 kV", "132/11 kV and 33/11 kV", "400/11 kV only", "66/22 kV" ], "answer": 1, "explanation": "Dubai uses 132/11 kV; Abu Dhabi and Sharjah also use 33/11 kV.", "ref": "" }, { "id": "MV501-044", "module": "MV-501", "level": "E", "region": "All", "question": "What happens to the healthy phase voltages on a solidly earthed system during an earth fault?", "options": [ "They drop to zero", "They rise to 1.73 pu", "They stay at or below about 1.4 pu", "They reverse" ], "answer": 2, "explanation": "Effectively earthed systems have an earth fault factor up to about 1.4.", "ref": "" }, { "id": "MV501-045", "module": "MV-501", "level": "B", "region": "All", "question": "Which part of the network do most building engineers deal with directly?", "options": [ "The power station", "400 kV transmission", "The 11 kV RMU, transformer and LV board in the building substation", "The HVDC link" ], "answer": 2, "explanation": "The consumer substation is the interface with the utility.", "ref": "" }, { "id": "MV501-046", "module": "MV-501", "level": "P", "region": "All", "question": "What is the benefit of automating an open ring with remote RMUs?", "options": [ "Restoration in about a minute instead of an hour", "No need for protection", "No faults", "Lower cable cost" ], "answer": 0, "explanation": "FLISR isolates and restores automatically.", "ref": "" }, { "id": "MV501-047", "module": "MV-501", "level": "E", "region": "All", "question": "In FLISR, what tells the software which section has the fault?", "options": [ "Energy meters", "Weather data", "Customer calls only", "Fault passage indicator data from the RMUs" ], "answer": 3, "explanation": "FPIs upstream of the fault flag, those downstream do not.", "ref": "" }, { "id": "MV501-048", "module": "MV-501", "level": "B", "region": "All", "question": "What colour is often used for \"live\" on network diagrams in this lab?", "options": [ "Green", "Blue", "Orange", "Grey" ], "answer": 2, "explanation": "Live is orange, earthed is green, dead is grey in MEPVirtual labs.", "ref": "" }, { "id": "MV502-001", "module": "MV-502", "level": "B", "region": "All", "question": "What is the job of the semiconducting conductor screen?", "options": [ "Keep water out", "Smooth the electric field around the strands", "Carry fault current", "Add strength" ], "answer": 1, "explanation": "It removes stress points from the stranded surface.", "ref": "" }, { "id": "MV502-002", "module": "MV-502", "level": "B", "region": "All", "question": "What is the nominal XLPE insulation thickness for an 11 kV (6.35/11 kV) cable?", "options": [ "2.5 mm", "3.4 mm", "8.0 mm", "5.5 mm" ], "answer": 1, "explanation": "IEC 60502-2 gives 3.4 mm for 6/10 (12) kV cables.", "ref": "IEC 60502-2" }, { "id": "MV502-003", "module": "MV-502", "level": "B", "region": "All", "question": "What is the maximum continuous conductor temperature for XLPE?", "options": [ "70 °C", "105 °C", "90 °C", "250 °C" ], "answer": 2, "explanation": "XLPE is rated 90 °C continuous and 250 °C short-circuit.", "ref": "" }, { "id": "MV502-004", "module": "MV-502", "level": "B", "region": "All", "question": "What is the short-circuit temperature limit for XLPE insulation?", "options": [ "250 °C", "200 °C", "350 °C", "160 °C" ], "answer": 0, "explanation": "250 °C for a short time.", "ref": "" }, { "id": "MV502-005", "module": "MV-502", "level": "B", "region": "All", "question": "Why do single-core cables use aluminium wire armour?", "options": [ "Steel would heat up in the single-core magnetic field", "Cheaper", "Aluminium is stronger", "Steel rusts" ], "answer": 0, "explanation": "Magnetic armour around a single conductor causes large losses.", "ref": "" }, { "id": "MV502-006", "module": "MV-502", "level": "B", "region": "All", "question": "What does the copper wire screen carry?", "options": [ "Data", "Load current", "Charging and earth fault current", "Nothing" ], "answer": 2, "explanation": "It keeps the cable surface at earth potential and returns fault current.", "ref": "" }, { "id": "MV502-007", "module": "MV-502", "level": "B", "region": "All", "question": "Which oversheath is preferred where smoke and toxic fumes matter, such as in buildings?", "options": [ "Bitumen", "LSZH", "PVC", "PE" ], "answer": 1, "explanation": "Low smoke zero halogen (BS 7835 in UK and GCC practice).", "ref": "" }, { "id": "MV502-008", "module": "MV-502", "level": "B", "region": "All", "question": "For XLPE copper conductors (90 to 250 °C), k in A = I√t/k is about...", "options": [ "226", "143", "115", "94" ], "answer": 1, "explanation": "k ≈ 143 for Cu and 94 for Al.", "ref": "IEC 60949" }, { "id": "MV502-009", "module": "MV-502", "level": "B", "region": "All", "question": "A 25 kA fault cleared in 1 s needs at least what copper area?", "options": [ "150 mm²", "240 mm²", "185 mm²", "95 mm²" ], "answer": 2, "explanation": "25,000/143 = 175 mm², next standard size 185 mm².", "ref": "" }, { "id": "MV502-010", "module": "MV-502", "level": "B", "region": "All", "question": "Which usually has the biggest effect on a buried cable rating?", "options": [ "Lug type", "Phase sequence", "Soil thermal resistance", "Colour" ], "answer": 2, "explanation": "Most heat must pass through the soil.", "ref": "" }, { "id": "MV502-011", "module": "MV-502", "level": "B", "region": "GCC", "question": "Why are GCC cable ratings often lower than European tables?", "options": [ "Lower voltage", "No sunlight", "Better soil", "Dry sand and high ground temperatures" ], "answer": 3, "explanation": "High soil resistivity and 35 °C ground cut the rating.", "ref": "" }, { "id": "MV502-012", "module": "MV-502", "level": "P", "region": "All", "question": "Which standard is the reference method for cable current rating?", "options": [ "IEC 61850", "IEC 60287", "IEC 60364", "IEC 60909" ], "answer": 1, "explanation": "IEC 60287 covers steady-state current ratings.", "ref": "" }, { "id": "MV502-013", "module": "MV-502", "level": "P", "region": "All", "question": "What is T4 in IEC 60287?", "options": [ "Ambient temperature", "Armour loss", "External (soil or air) thermal resistance", "Insulation thermal resistance" ], "answer": 2, "explanation": "T4 is usually the largest term for buried cables.", "ref": "" }, { "id": "MV502-014", "module": "MV-502", "level": "P", "region": "All", "question": "What is the main downside of bonding single-core screens at both ends?", "options": [ "Standing voltage", "Circulating currents that heat the cable", "No earth", "Needs link boxes" ], "answer": 1, "explanation": "Both-ends bonding lets induced currents circulate.", "ref": "" }, { "id": "MV502-015", "module": "MV-502", "level": "P", "region": "All", "question": "What is fitted at the open end of a single-point bonded cable?", "options": [ "Nothing", "A capacitor", "A sheath voltage limiter (SVL)", "A fuse" ], "answer": 2, "explanation": "SVLs limit screen voltage during faults and surges.", "ref": "" }, { "id": "MV502-016", "module": "MV-502", "level": "P", "region": "All", "question": "Cross bonding uses how many minor sections per major section?", "options": [ "3", "2", "4", "6" ], "answer": 0, "explanation": "Screens are transposed at two link boxes between three minor sections.", "ref": "" }, { "id": "MV502-017", "module": "MV-502", "level": "P", "region": "All", "question": "Many utilities limit standing voltage under full load to about...", "options": [ "500 V", "1 kV", "5 V", "50 to 65 V" ], "answer": 3, "explanation": "Check the utility limit, often in this range.", "ref": "" }, { "id": "MV502-018", "module": "MV-502", "level": "P", "region": "All", "question": "What is the typical minimum installed bending radius for single-core MV cable?", "options": [ "5 × D", "50 × D", "15 × D", "100 × D" ], "answer": 2, "explanation": "Often 15 × D for single-core and 12 × D for three-core. Check the manufacturer.", "ref": "" }, { "id": "MV502-019", "module": "MV-502", "level": "P", "region": "All", "question": "Why must the semicon cut be square and clean at a termination?", "options": [ "Appearance", "For the lug", "For earthing", "The field concentrates at the screen edge" ], "answer": 3, "explanation": "Nicks and steps start PD and tracking.", "ref": "" }, { "id": "MV502-020", "module": "MV-502", "level": "B", "region": "All", "question": "Why is stress control needed at a termination?", "options": [ "The field crowds where the insulation screen stops", "Water sealing", "For earthing", "To hold the lug" ], "answer": 0, "explanation": "Stress tubes or cones spread the field.", "ref": "" }, { "id": "MV502-021", "module": "MV-502", "level": "B", "region": "All", "question": "When cleaning XLPE insulation before fitting a termination, which way should you wipe?", "options": [ "Circles", "Any way", "Away from the semicon", "Towards the semicon" ], "answer": 2, "explanation": "Avoids dragging carbon onto the insulation.", "ref": "" }, { "id": "MV502-022", "module": "MV-502", "level": "P", "region": "All", "question": "What do outdoor terminations add compared with indoor ones?", "options": [ "Armour", "Rain sheds for creepage", "Lugs", "Fuses" ], "answer": 1, "explanation": "Sheds increase the creepage path in wet and polluted conditions.", "ref": "" }, { "id": "MV502-023", "module": "MV-502", "level": "P", "region": "GCC", "question": "Why do coastal GCC sites need higher creepage terminations?", "options": [ "Low temperature", "Salt and dust pollution", "No rain", "Low humidity" ], "answer": 1, "explanation": "Pollution causes surface tracking.", "ref": "" }, { "id": "MV502-024", "module": "MV-502", "level": "P", "region": "All", "question": "What does a three-core MV cable have around each core?", "options": [ "AWA", "No screen", "Copper tape screen", "Lead sheath always" ], "answer": 2, "explanation": "Each core has its own metallic screen.", "ref": "" }, { "id": "MV502-025", "module": "MV-502", "level": "P", "region": "AU", "question": "Which standard covers MV polymeric cables in Australia and NZ?", "options": [ "AS/NZS 4777", "AS/NZS 3008", "AS/NZS 1429.1", "AS 2067" ], "answer": 2, "explanation": "AS/NZS 3008 covers LV cable selection.", "ref": "" }, { "id": "MV502-026", "module": "MV-502", "level": "P", "region": "Asia", "question": "Which Indian standard covers XLPE MV cables?", "options": [ "IS 1180", "IS 7098-2", "IS 732", "IS 3043" ], "answer": 1, "explanation": "IS 7098 Part 2 covers 3.3 to 33 kV XLPE cables.", "ref": "" }, { "id": "MV502-027", "module": "MV-502", "level": "E", "region": "All", "question": "In IEC 60287, what does λ1 represent?", "options": [ "Screen loss factor", "Dielectric loss", "Ambient", "Armour thermal resistance" ], "answer": 0, "explanation": "Ratio of screen losses to conductor losses.", "ref": "" }, { "id": "MV502-028", "module": "MV-502", "level": "E", "region": "All", "question": "Why is dielectric loss more important at 33 kV than 11 kV?", "options": [ "It scales with U0²", "It depends on soil", "It depends on current", "It is not" ], "answer": 0, "explanation": "Wd = ωCU0² tanδ.", "ref": "" }, { "id": "MV502-029", "module": "MV-502", "level": "E", "region": "All", "question": "Which installation usually rates higher for the same cable?", "options": [ "Under a hot pipe", "In free air shaded on a tray", "In a crowded duct bank", "Buried in dry sand" ], "answer": 1, "explanation": "Free air convection removes heat well when shaded.", "ref": "" }, { "id": "MV502-030", "module": "MV-502", "level": "E", "region": "All", "question": "For a long route, which section sets the circuit rating?", "options": [ "The termination", "The hottest or worst-cooled section", "The first metre", "The average section" ], "answer": 1, "explanation": "Rate the most onerous section, such as a road crossing.", "ref": "" }, { "id": "MV502-031", "module": "MV-502", "level": "P", "region": "All", "question": "Grouping several buried circuits close together...", "options": [ "Only matters in air", "Lowers each rating through mutual heating", "Raises each rating", "Has no effect" ], "answer": 1, "explanation": "Apply group derating factors.", "ref": "" }, { "id": "MV502-032", "module": "MV-502", "level": "B", "region": "All", "question": "What is the most common MV ring cable arrangement in GCC cities?", "options": [ "Gas insulated lines", "Overhead lines", "Single-core or three-core XLPE underground cables", "Aluminium busbars" ], "answer": 2, "explanation": "Urban MV networks are underground.", "ref": "" }, { "id": "MV502-033", "module": "MV-502", "level": "P", "region": "All", "question": "What VLF frequency is normally used for cable testing?", "options": [ "0.1 Hz", "10 Hz", "50 Hz", "DC only" ], "answer": 0, "explanation": "0.1 Hz reduces the test set size dramatically.", "ref": "" }, { "id": "MV502-034", "module": "MV-502", "level": "P", "region": "All", "question": "Why are screens earthed at terminations?", "options": [ "To carry load", "For lighting", "To reduce weight", "To keep the screen at earth and give a fault return path" ], "answer": 3, "explanation": "Except at the SVL end of single-point bonding.", "ref": "" }, { "id": "MV502-035", "module": "MV-502", "level": "E", "region": "All", "question": "Standing voltage per km on single-point bonded trefoil cables at 400 A is roughly...", "options": [ "20 V", "2 kV", "20 kV", "0.2 V" ], "answer": 0, "explanation": "Around 50 V/km/kA for touching trefoil, so about 20 V/km at 400 A.", "ref": "" }, { "id": "MV502-036", "module": "MV-502", "level": "B", "region": "All", "question": "What is the conductor standard for MV cables?", "options": [ "IEC 60909", "IEC 61439", "IEC 60228", "IEC 60076" ], "answer": 2, "explanation": "IEC 60228 class 2 stranded conductors.", "ref": "" }, { "id": "MV502-037", "module": "MV-502", "level": "P", "region": "All", "question": "Aluminium conductors need about how much more area than copper for the same current?", "options": [ "Same", "About 1.6 times", "10%", "3 times" ], "answer": 1, "explanation": "Aluminium has higher resistivity.", "ref": "" }, { "id": "MV502-038", "module": "MV-502", "level": "P", "region": "All", "question": "Why is triple extrusion used for MV cables?", "options": [ "Speed", "Avoids voids and contamination between the screens and insulation", "Colour", "Cheaper armour" ], "answer": 1, "explanation": "Interfaces are where PD starts.", "ref": "" }, { "id": "MV502-039", "module": "MV-502", "level": "E", "region": "All", "question": "What allows a sheath integrity test after laying?", "options": [ "The lug", "Armour", "A semiconducting or graphite coating on the oversheath", "The conductor" ], "answer": 2, "explanation": "The coating acts as an outer electrode for the DC test.", "ref": "" }, { "id": "MV502-040", "module": "MV-502", "level": "B", "region": "All", "question": "Which voltage drop is usually small for MV feeders?", "options": [ "LV final circuit drop", "None", "MV voltage drop", "Busbar drop" ], "answer": 2, "explanation": "MV currents are low, so drop is usually small unless very long.", "ref": "" }, { "id": "MV502-041", "module": "MV-502", "level": "P", "region": "All", "question": "What does the 3U0 in a VLF test of an 11 kV cable equal?", "options": [ "33 kV", "19 kV rms", "6.35 kV", "11 kV" ], "answer": 1, "explanation": "3 × 6.35 ≈ 19 kV.", "ref": "" }, { "id": "MV502-042", "module": "MV-502", "level": "E", "region": "All", "question": "Why might ducted single-core cables rate close to direct buried in a simple IEC 60287 model?", "options": [ "Ducts carry current", "Larger duct diameters spread heat while duct air adds resistance", "No reason", "Ducts cool better" ], "answer": 1, "explanation": "Real duct banks often rate lower due to grouping and poor backfill.", "ref": "" }, { "id": "MV502-043", "module": "MV-502", "level": "B", "region": "All", "question": "What colour oversheath is common for MV cables in UK and GCC practice?", "options": [ "Green", "Blue", "Red", "Yellow" ], "answer": 2, "explanation": "Red oversheaths are common for MV.", "ref": "" }, { "id": "MV502-044", "module": "MV-502", "level": "P", "region": "All", "question": "What is the purpose of water blocking in MV cables?", "options": [ "Stop water travelling along the cable if it is damaged", "Cooling", "Earthing", "Increase rating" ], "answer": 0, "explanation": "Longitudinal water blocking limits damage.", "ref": "" }, { "id": "MV502-045", "module": "MV-502", "level": "P", "region": "All", "question": "Which oversheath material has the lowest thermal resistivity in the lab model?", "options": [ "PE", "Rubber", "PVC", "LSZH" ], "answer": 0, "explanation": "PE is taken as 3.5 K·m/W, PVC as 5.0.", "ref": "" }, { "id": "MV502-046", "module": "MV-502", "level": "E", "region": "All", "question": "What causes eddy current losses in the screen?", "options": [ "Low frequency", "Moisture", "The magnetic field of nearby conductors", "DC current" ], "answer": 2, "explanation": "Eddy losses are small for wire screens and are ignored in the lab model.", "ref": "" }, { "id": "MV502-047", "module": "MV-502", "level": "B", "region": "All", "question": "Which test is done on the oversheath after laying?", "options": [ "Secondary injection", "Tan delta", "Turns ratio", "Sheath integrity (DC) test" ], "answer": 3, "explanation": "Finds sheath damage that would let water in.", "ref": "" }, { "id": "MV503-001", "module": "MV-503", "level": "B", "region": "All", "question": "What does RMU stand for?", "options": [ "Rated Medium Unit", "Relay Main Unit", "Remote Monitoring Unit", "Ring Main Unit" ], "answer": 3, "explanation": "Compact MV switchgear for ring networks.", "ref": "" }, { "id": "MV503-002", "module": "MV-503", "level": "B", "region": "All", "question": "In a CCF RMU, what does F stand for?", "options": [ "Fixed earth", "Fuse-switch combination", "Fault indicator", "Feeder breaker" ], "answer": 1, "explanation": "C is a cable switch, F a fuse-switch, V a vacuum breaker.", "ref": "" }, { "id": "MV503-003", "module": "MV-503", "level": "B", "region": "All", "question": "On a three-position switch, which move is blocked?", "options": [ "Closed straight to earthed", "Open to earthed", "Earthed to open", "Open to closed" ], "answer": 0, "explanation": "It must pass through OPEN.", "ref": "" }, { "id": "MV503-004", "module": "MV-503", "level": "B", "region": "All", "question": "When can the cable compartment cover be removed?", "options": [ "When VPIS is lit", "Only when the earthing switch is closed", "After resetting the relay", "Any time" ], "answer": 1, "explanation": "Cover is interlocked with the earth switch.", "ref": "" }, { "id": "MV503-005", "module": "MV-503", "level": "B", "region": "All", "question": "What rated voltage is used on an 11 kV system?", "options": [ "24 kV", "17.5 kV", "11 kV", "12 kV" ], "answer": 3, "explanation": "IEC 62271-1 standard value.", "ref": "IEC 62271-1" }, { "id": "MV503-006", "module": "MV-503", "level": "B", "region": "All", "question": "What does LSC2 tell you?", "options": [ "Busbar and other units stay in service when one compartment is opened", "SF6", "2 s rating", "Two switches" ], "answer": 0, "explanation": "Loss of service continuity category.", "ref": "IEC 62271-200" }, { "id": "MV503-007", "module": "MV-503", "level": "B", "region": "All", "question": "In IAC AFL 20 kA 1 s, what does A mean?", "options": [ "Automatic", "Accessibility restricted to authorised personnel", "Arc current", "Air insulated" ], "answer": 1, "explanation": "B is for public accessibility.", "ref": "" }, { "id": "MV503-008", "module": "MV-503", "level": "B", "region": "All", "question": "Before earthing a ring cable, what is most important?", "options": [ "Reset the relay", "Close the busbar", "Prove dead on the VPIS and confirm the far end is open", "Remove the cover" ], "answer": 2, "explanation": "Interlocks cannot see the far end.", "ref": "" }, { "id": "MV503-009", "module": "MV-503", "level": "B", "region": "All", "question": "Peak withstand Ip at 50 Hz for 20 kA is...", "options": [ "50 kA", "52 kA", "40 kA", "20 kA" ], "answer": 0, "explanation": "Ip = 2.5 × Ik at 50 Hz.", "ref": "" }, { "id": "MV503-010", "module": "MV-503", "level": "B", "region": "All", "question": "What is the FLC of a 1000 kVA transformer at 11 kV?", "options": [ "91 A", "52.5 A", "26 A", "1443 A" ], "answer": 1, "explanation": "1000/(1.732 × 11).", "ref": "" }, { "id": "MV503-011", "module": "MV-503", "level": "B", "region": "All", "question": "What does the fuse striker do?", "options": [ "Lights VPIS", "Earths the transformer", "Trips the switch on all three phases when a fuse blows", "Resets the relay" ], "answer": 2, "explanation": "Stops single phasing.", "ref": "" }, { "id": "MV503-012", "module": "MV-503", "level": "B", "region": "All", "question": "What does VPIS show?", "options": [ "Temperature", "Voltage presence on the cable", "Energy", "Gas pressure" ], "answer": 1, "explanation": "Voltage presence indicating system.", "ref": "IEC 62271-213" }, { "id": "MV503-013", "module": "MV-503", "level": "P", "region": "All", "question": "Which standard covers switch-fuse combinations?", "options": [ "IEC 60282-1", "IEC 62271-105", "IEC 62271-102", "IEC 62271-100" ], "answer": 1, "explanation": "IEC 62271-105.", "ref": "" }, { "id": "MV503-014", "module": "MV-503", "level": "P", "region": "All", "question": "Which standard covers earthing switches?", "options": [ "IEC 60502", "IEC 62271-102", "IEC 62271-103", "IEC 60076" ], "answer": 1, "explanation": "Disconnectors and earthing switches.", "ref": "" }, { "id": "MV503-015", "module": "MV-503", "level": "P", "region": "All", "question": "Earthing switch class E2 means...", "options": [ "Indoor only", "No making capacity", "2 kA rating", "Can make onto a short circuit twice without maintenance" ], "answer": 3, "explanation": "Important if someone earths a live circuit.", "ref": "" }, { "id": "MV503-016", "module": "MV-503", "level": "P", "region": "All", "question": "Fuse-switch combinations are common for transformers up to about...", "options": [ "315 kVA", "1000 to 1250 kVA at 11 kV", "20 MVA", "5 MVA" ], "answer": 1, "explanation": "Above this, CBs with relays are typical.", "ref": "" }, { "id": "MV503-017", "module": "MV-503", "level": "P", "region": "All", "question": "On a breaker (V) unit, when can the disconnector be operated?", "options": [ "Only with the CB open", "Only with the CB closed", "Only remotely", "Any time" ], "answer": 0, "explanation": "Disconnectors are not load-breaking devices.", "ref": "" }, { "id": "MV503-018", "module": "MV-503", "level": "P", "region": "All", "question": "Which IAC class suits a public pad-mount kiosk?", "options": [ "B", "A", "None", "C" ], "answer": 0, "explanation": "Accessibility B covers public areas.", "ref": "" }, { "id": "MV503-019", "module": "MV-503", "level": "P", "region": "All", "question": "What is the 12 kV lightning impulse withstand level (list 2)?", "options": [ "75 kV", "60 kV", "28 kV", "125 kV" ], "answer": 0, "explanation": "12 kV: Ud 28 kV, Up 75 kV.", "ref": "IEC 62271-1" }, { "id": "MV503-020", "module": "MV-503", "level": "P", "region": "All", "question": "What is the 24 kV power frequency withstand (Ud)?", "options": [ "28 kV", "70 kV", "50 kV", "125 kV" ], "answer": 2, "explanation": "24 kV: Ud 50 kV, Up 125 kV.", "ref": "" }, { "id": "MV503-021", "module": "MV-503", "level": "P", "region": "All", "question": "From which year does the EU ban SF6 in new MV switchgear up to 24 kV (with exceptions)?", "options": [ "2026", "2022", "2030", "2035" ], "answer": 0, "explanation": "Regulation (EU) 2024/573: up to 24 kV from 2026, up to 52 kV from 2030.", "ref": "" }, { "id": "MV503-022", "module": "MV-503", "level": "P", "region": "All", "question": "What do SF6-free RMUs typically use?", "options": [ "Oil", "Vacuum interrupters with clean air, dry air or solid insulation", "CO2 arcs", "Hydrogen" ], "answer": 1, "explanation": "Vacuum does the switching.", "ref": "" }, { "id": "MV503-023", "module": "MV-503", "level": "P", "region": "All", "question": "What must a transformer fuse withstand without blowing?", "options": [ "Nothing", "LV fault current", "Magnetising inrush, about 10 to 12 × In for 0.1 s", "Load current only" ], "answer": 2, "explanation": "Use the maker selection table.", "ref": "" }, { "id": "MV503-024", "module": "MV-503", "level": "P", "region": "All", "question": "Typical rated current for RMU ring switches and busbars is...", "options": [ "2500 A", "200 A", "400 A", "630 A" ], "answer": 3, "explanation": "630 A is standard.", "ref": "" }, { "id": "MV503-025", "module": "MV-503", "level": "E", "region": "All", "question": "Why might IAC not apply as installed?", "options": [ "Room size or gas exhaust path differs from the tested arrangement", "Wrong voltage", "Too many units", "Wrong colour" ], "answer": 0, "explanation": "Check minimum room dimensions and relief direction.", "ref": "" }, { "id": "MV503-026", "module": "MV-503", "level": "E", "region": "All", "question": "At 60 Hz, peak withstand Ip equals...", "options": [ "2.5 × Ik", "2.2 × Ik", "1.8 × Ik", "2.6 × Ik" ], "answer": 3, "explanation": "IEC 62271-1.", "ref": "" }, { "id": "MV503-027", "module": "MV-503", "level": "E", "region": "All", "question": "What happens if an E2 earthing switch is closed onto a live cable?", "options": [ "Nothing", "A fault is made; the switch survives but the source breaker trips", "The cable is safe", "The VPIS resets" ], "answer": 1, "explanation": "A serious operating error even if the equipment survives.", "ref": "" }, { "id": "MV503-028", "module": "MV-503", "level": "B", "region": "All", "question": "What is the purpose of a padlock on the operating aperture?", "options": [ "To stop anyone operating the switch during work", "Decoration", "To measure", "To earth the unit" ], "answer": 0, "explanation": "Part of lock out tag out.", "ref": "" }, { "id": "MV503-029", "module": "MV-503", "level": "B", "region": "All", "question": "Where do hot gases go during an internal arc in an IAC tested RMU?", "options": [ "Out the front", "Into the LV board", "Nowhere", "Through the pressure relief duct away from the operator" ], "answer": 3, "explanation": "Usually down to the trench or to the rear.", "ref": "" }, { "id": "MV503-030", "module": "MV-503", "level": "P", "region": "All", "question": "LV back-feed from a generator can make which RMU circuit live?", "options": [ "The busbar only", "Ring cable only", "The transformer feeder even with its MV switch open", "Nothing" ], "answer": 2, "explanation": "Open the LV main before earthing the transformer feeder.", "ref": "" }, { "id": "MV503-031", "module": "MV-503", "level": "B", "region": "All", "question": "Which unit letter means a vacuum circuit breaker feeder?", "options": [ "V", "D", "F", "C" ], "answer": 0, "explanation": "V units have a relay.", "ref": "" }, { "id": "MV503-032", "module": "MV-503", "level": "P", "region": "All", "question": "What does a metering unit (M) in switchgear contain?", "options": [ "Only a switch", "Capacitors", "Fuses", "CTs and VTs for MV metering" ], "answer": 3, "explanation": "For bulk supply customers.", "ref": "" }, { "id": "MV503-033", "module": "MV-503", "level": "P", "region": "GCC", "question": "What should be checked before specifying an RMU make in the GCC?", "options": [ "Weight only", "Colour", "Whether it is on the utility approved list", "Paint thickness" ], "answer": 2, "explanation": "Utilities only accept approved models.", "ref": "" }, { "id": "MV503-034", "module": "MV-503", "level": "P", "region": "GCC", "question": "Which ambient is typical for GCC switchgear specifications?", "options": [ "40 °C", "60 °C", "25 °C", "Up to 50 °C" ], "answer": 3, "explanation": "Rate and derate for high ambient.", "ref": "" }, { "id": "MV503-035", "module": "MV-503", "level": "P", "region": "AU", "question": "Which Australian standard matches IEC 62271-200?", "options": [ "AS 1429", "AS 62271.200", "AS 2067", "AS 3000" ], "answer": 1, "explanation": "AS 62271.200 is identical.", "ref": "" }, { "id": "MV503-036", "module": "MV-503", "level": "P", "region": "NZ", "question": "Which seismic standard applies to RMU restraint in NZ?", "options": [ "IEC 60909", "NZS 1170.5 / NZS 4219", "AS 2067", "IEEE 80" ], "answer": 1, "explanation": "Design restraints for earthquakes.", "ref": "" }, { "id": "MV503-037", "module": "MV-503", "level": "E", "region": "All", "question": "A switch class E3 refers to...", "options": [ "Explosion class", "Electrical endurance of a general-purpose switch", "Enclosure class", "Earthing switch class" ], "answer": 1, "explanation": "IEC 62271-103 electrical endurance.", "ref": "" }, { "id": "MV503-038", "module": "MV-503", "level": "E", "region": "All", "question": "Why prove the VPIS indicator before and after use?", "options": [ "To be sure a dark reading really means dead", "To earth it", "Habit only", "To charge it" ], "answer": 0, "explanation": "A failed indicator could show dead on a live circuit.", "ref": "" }, { "id": "MV503-039", "module": "MV-503", "level": "B", "region": "All", "question": "What is a typical position indicator colour for \"closed\" in this lab?", "options": [ "Yellow", "Red", "Green", "Blue" ], "answer": 1, "explanation": "Closed red, open green, earthed yellow.", "ref": "" }, { "id": "MV503-040", "module": "MV-503", "level": "P", "region": "All", "question": "Which fuse standard applies to current-limiting HV fuses?", "options": [ "IEC 62271-100", "IEC 60898", "IEC 60269", "IEC 60282-1" ], "answer": 3, "explanation": "IEC 60282-1.", "ref": "" }, { "id": "MV503-041", "module": "MV-503", "level": "P", "region": "All", "question": "A 1250 kVA 11 kV transformer feeder fuse would typically be around...", "options": [ "1 kA", "100 A", "16 A", "400 A" ], "answer": 1, "explanation": "FLC 65.6 A, so about 100 A from typical tables.", "ref": "" }, { "id": "MV503-042", "module": "MV-503", "level": "E", "region": "All", "question": "Which is NOT controlled by the RMU mechanical interlocks?", "options": [ "Whether the far end of the cable is live", "Fuse access before earthing", "Cover removal before earthing", "Earthing from closed" ], "answer": 0, "explanation": "That is why switching programs coordinate both ends.", "ref": "" }, { "id": "MV503-043", "module": "MV-503", "level": "B", "region": "All", "question": "What insulation medium is in a sealed SF6 RMU tank?", "options": [ "Air at atmospheric pressure", "Oil", "Water", "SF6 gas" ], "answer": 3, "explanation": "Sealed for life.", "ref": "" }, { "id": "MV503-044", "module": "MV-503", "level": "P", "region": "All", "question": "What should the gas pressure gauge show before energising?", "options": [ "Zero", "Red zone", "Green zone", "Any reading" ], "answer": 2, "explanation": "Low pressure reduces insulation level.", "ref": "" }, { "id": "MV503-045", "module": "MV-503", "level": "B", "region": "All", "question": "How many ring switches does a standard CCF RMU have?", "options": [ "3", "1", "2", "4" ], "answer": 2, "explanation": "Two C units.", "ref": "" }, { "id": "MV503-046", "module": "MV-503", "level": "P", "region": "All", "question": "A CCCF RMU has how many cable switches?", "options": [ "1", "4", "3", "2" ], "answer": 2, "explanation": "Three C units plus one F.", "ref": "" }, { "id": "MV503-047", "module": "MV-503", "level": "E", "region": "All", "question": "Which relay functions are typical on a V unit protecting a transformer?", "options": [ "27", "50/51 and 50N/51N", "21", "87B only" ], "answer": 1, "explanation": "Overcurrent and earth fault, often self-powered.", "ref": "" }, { "id": "MV503-048", "module": "MV-503", "level": "P", "region": "All", "question": "Why are anti-condensation heaters fitted in RMU cable compartments?", "options": [ "For lighting", "For comfort", "To heat SF6", "To prevent moisture and tracking" ], "answer": 3, "explanation": "Important in humid and coastal sites.", "ref": "" }, { "id": "MV503-049", "module": "MV-503", "level": "B", "region": "All", "question": "What should happen after replacing blown fuses?", "options": [ "Re-energise immediately", "Find the cause of the fault first", "Remove the striker", "Nothing" ], "answer": 1, "explanation": "Fuses blow for a reason.", "ref": "" }, { "id": "MV504-001", "module": "MV-504", "level": "B", "region": "All", "question": "In Dyn11, what does 11 mean?", "options": [ "11 kV", "11 taps", "LV lags by 11°", "LV leads HV by 30°" ], "answer": 3, "explanation": "Clock number × 30°, 11 o'clock = 30° lead.", "ref": "" }, { "id": "MV504-002", "module": "MV-504", "level": "B", "region": "All", "question": "LV full-load current of a 1000 kVA transformer at 400 V is...", "options": [ "1443 A", "1000 A", "252 A", "2500 A" ], "answer": 0, "explanation": "1,000,000/(1.732 × 400).", "ref": "" }, { "id": "MV504-003", "module": "MV-504", "level": "B", "region": "All", "question": "Which pair can safely run in parallel?", "options": [ "Dyn11 and Yyn0", "Dyn1 and Dyn5", "Dyn11 and Yzn11", "Dyn11 and Dyn1" ], "answer": 2, "explanation": "Same clock number.", "ref": "" }, { "id": "MV504-004", "module": "MV-504", "level": "B", "region": "All", "question": "IEC 60076-5 minimum impedance for a 1600 kVA transformer is...", "options": [ "5%", "4%", "7.15%", "6.25%" ], "answer": 3, "explanation": "1251 to 2500 kVA: 6.25%.", "ref": "" }, { "id": "MV504-005", "module": "MV-504", "level": "B", "region": "All", "question": "When is a transformer most efficient?", "options": [ "Full load", "When load losses equal no-load losses", "No load", "120% load" ], "answer": 1, "explanation": "At √(P0/Pk) of rated load.", "ref": "" }, { "id": "MV504-006", "module": "MV-504", "level": "B", "region": "All", "question": "Which losses are present even at no load?", "options": [ "Core (no-load) losses", "None", "Stray losses", "Copper losses" ], "answer": 0, "explanation": "The core is magnetised whenever energised.", "ref": "" }, { "id": "MV504-007", "module": "MV-504", "level": "B", "region": "All", "question": "Paper ageing doubles for every how many K above 98 °C hot spot?", "options": [ "6 K", "3 K", "20 K", "10 K" ], "answer": 0, "explanation": "V = 2^((θh − 98)/6).", "ref": "IEC 60076-7" }, { "id": "MV504-008", "module": "MV-504", "level": "B", "region": "All", "question": "Why are cast resin transformers used inside buildings?", "options": [ "Lower losses", "No flammable oil, self-extinguishing", "Higher impedance", "Cheaper" ], "answer": 1, "explanation": "Fire class F1.", "ref": "" }, { "id": "MV504-009", "module": "MV-504", "level": "B", "region": "All", "question": "What does a Buchholz relay detect?", "options": [ "Earth leakage", "Phase sequence", "Gas and oil surges from internal faults", "LV overload" ], "answer": 2, "explanation": "Fitted in the conservator pipe.", "ref": "" }, { "id": "MV504-010", "module": "MV-504", "level": "B", "region": "All", "question": "What does a silica gel breather do?", "options": [ "Measures load", "Cools oil", "Dries air entering the conservator", "Earths the tank" ], "answer": 2, "explanation": "Gel changes colour when wet.", "ref": "" }, { "id": "MV504-011", "module": "MV-504", "level": "B", "region": "All", "question": "What does ONAN mean?", "options": [ "Oil Natural Air Natural", "Oil Nitrogen Air Nitrogen", "On Neutral Always Neutral", "Oil Normal Air Normal" ], "answer": 0, "explanation": "Natural circulation cooling.", "ref": "" }, { "id": "MV504-012", "module": "MV-504", "level": "B", "region": "All", "question": "Typical off-circuit tap range on distribution transformers is...", "options": [ "None", "±10 × 1%", "±20%", "±2 × 2.5%" ], "answer": 3, "explanation": "Five positions.", "ref": "" }, { "id": "MV504-013", "module": "MV-504", "level": "P", "region": "All", "question": "When may an off-circuit tap changer be operated?", "options": [ "On load only", "During faults", "Any time", "Only with the transformer de-energised" ], "answer": 3, "explanation": "Operating it energised can arc and damage contacts.", "ref": "" }, { "id": "MV504-014", "module": "MV-504", "level": "P", "region": "All", "question": "Approximate LV fault level of a 2000 kVA, 6.25% transformer at 400 V (infinite source)?", "options": [ "12 kA", "46 kA", "26 kA", "80 kA" ], "answer": 1, "explanation": "2887/0.0625 ≈ 46 kA.", "ref": "" }, { "id": "MV504-015", "module": "MV-504", "level": "P", "region": "All", "question": "What is the IEC 60076-2 maximum ambient assumption?", "options": [ "50 °C", "40 °C", "30 °C", "20 °C" ], "answer": 1, "explanation": "40 °C max, 30 °C monthly average, 20 °C yearly average.", "ref": "" }, { "id": "MV504-016", "module": "MV-504", "level": "P", "region": "GCC", "question": "At a 50 °C site, how much should the allowed temperature rise be reduced?", "options": [ "10 K", "5 K", "20 K", "0 K" ], "answer": 0, "explanation": "By the excess over 40 °C.", "ref": "" }, { "id": "MV504-017", "module": "MV-504", "level": "P", "region": "All", "question": "Conditions for parallel operation include all EXCEPT...", "options": [ "Same phase shift", "Same ratio within about 0.5%", "Similar impedance", "Same paint colour" ], "answer": 3, "explanation": "Also same phase sequence.", "ref": "" }, { "id": "MV504-018", "module": "MV-504", "level": "P", "region": "All", "question": "What happens if two transformers with different clock numbers are paralleled?", "options": [ "Large circulating current like a short circuit", "Lower losses", "Nothing", "Better sharing" ], "answer": 0, "explanation": "Never parallel different phase shifts.", "ref": "" }, { "id": "MV504-019", "module": "MV-504", "level": "P", "region": "All", "question": "The lower impedance transformer in a parallel pair...", "options": [ "Takes more than its share", "Trips", "Takes none", "Takes less load" ], "answer": 0, "explanation": "Load shares inversely with per-unit impedance.", "ref": "" }, { "id": "MV504-020", "module": "MV-504", "level": "P", "region": "All", "question": "Why does the LV winding usually sit next to the core?", "options": [ "It needs less insulation to the earthed core", "Cooling", "For taps", "Cost only" ], "answer": 0, "explanation": "HV goes outside.", "ref": "" }, { "id": "MV504-021", "module": "MV-504", "level": "P", "region": "All", "question": "On which winding are the tappings placed?", "options": [ "HV", "Neither", "Both", "LV" ], "answer": 0, "explanation": "Lower current on HV.", "ref": "" }, { "id": "MV504-022", "module": "MV-504", "level": "P", "region": "AU", "question": "Which standard sets minimum energy performance of distribution transformers in AU/NZ?", "options": [ "AS 3000", "AS 4777", "AS 2374.1.2", "AS 1429" ], "answer": 2, "explanation": "MEPS for distribution transformers.", "ref": "" }, { "id": "MV504-023", "module": "MV-504", "level": "P", "region": "All", "question": "Which EU regulations set Ecodesign loss limits for transformers?", "options": [ "IEEE 519", "(EU) 2024/573", "(EU) 548/2014 and 2019/1783", "IEC 60909" ], "answer": 2, "explanation": "Tier 1 and Tier 2 limits.", "ref": "" }, { "id": "MV504-024", "module": "MV-504", "level": "P", "region": "All", "question": "What does DGPT2 stand for on sealed transformers?", "options": [ "Detection of Gas, Pressure and Temperature (2 thresholds)", "Digital Grid Power Test", "None", "Dual Gas Pressure Tank" ], "answer": 0, "explanation": "Integrated protection for hermetic units.", "ref": "" }, { "id": "MV504-025", "module": "MV-504", "level": "P", "region": "All", "question": "How much extra capacity can AF fans typically add to a cast resin transformer?", "options": [ "200%", "30 to 40%", "100%", "5%" ], "answer": 1, "explanation": "For peaks, not continuous design capacity.", "ref": "" }, { "id": "MV504-026", "module": "MV-504", "level": "P", "region": "All", "question": "Cast resin class F insulation has which thermal class?", "options": [ "155 °C", "130 °C", "180 °C", "105 °C" ], "answer": 0, "explanation": "Class H is 180 °C.", "ref": "" }, { "id": "MV504-027", "module": "MV-504", "level": "E", "region": "All", "question": "IEC 60076-7 normal cyclic loading limit for distribution transformer hot spot is...", "options": [ "98 °C", "140 °C", "160 °C", "120 °C" ], "answer": 3, "explanation": "Top oil 105 °C.", "ref": "" }, { "id": "MV504-028", "module": "MV-504", "level": "E", "region": "All", "question": "Which IEC 60076-7 parameter is the oil time constant for ONAN distribution transformers?", "options": [ "24 h", "30 min", "180 min", "4 min" ], "answer": 2, "explanation": "τo = 180 min, τw = 4 min.", "ref": "" }, { "id": "MV504-029", "module": "MV-504", "level": "E", "region": "All", "question": "What correction factor KT does IEC 60909 apply to network transformers?", "options": [ "1.0", "1/uk", "0.95 cmax/(1 + 0.6 xT)", "1.1" ], "answer": 2, "explanation": "Impedance correction factor.", "ref": "" }, { "id": "MV504-030", "module": "MV-504", "level": "E", "region": "All", "question": "Voltage regulation at full load is approximately...", "options": [ "ur cosφ + ux sinφ", "P0/Pk", "uk²", "1/uk" ], "answer": 0, "explanation": "Using per-unit resistance and reactance.", "ref": "" }, { "id": "MV504-031", "module": "MV-504", "level": "B", "region": "All", "question": "What is the standard distribution vector group in GCC, AU, NZ and the UK?", "options": [ "Yyn0", "Dyn11", "Dd0", "YNd1" ], "answer": 1, "explanation": "Delta HV, star LV with neutral.", "ref": "" }, { "id": "MV504-032", "module": "MV-504", "level": "P", "region": "All", "question": "Why is the HV winding often delta connected?", "options": [ "For taps", "Cheaper", "No reason", "Blocks triplen harmonics and gives a stable LV neutral" ], "answer": 3, "explanation": "Delta circulates triplen currents.", "ref": "" }, { "id": "MV504-033", "module": "MV-504", "level": "P", "region": "All", "question": "Which vector group suits small transformers with unbalanced single-phase loads?", "options": [ "YNd11", "Yzn11 or Dzn0", "Dd0", "Yyn0" ], "answer": 1, "explanation": "Zigzag handles unbalance well.", "ref": "" }, { "id": "MV504-034", "module": "MV-504", "level": "E", "region": "All", "question": "A 2500 kVA unit with a 6.25% impedance and a 25 kA 11 kV source gives LV fault at 400 V of about...", "options": [ "35 kA", "100 kA", "80 kA", "53 kA" ], "answer": 3, "explanation": "Source adds about 0.5% to the impedance.", "ref": "" }, { "id": "MV504-035", "module": "MV-504", "level": "B", "region": "All", "question": "What does a winding temperature indicator simulate?", "options": [ "Oil level", "Hot spot temperature using a CT-heated element", "Pressure", "Ambient" ], "answer": 1, "explanation": "Provides alarm and trip.", "ref": "" }, { "id": "MV504-036", "module": "MV-504", "level": "P", "region": "All", "question": "What do DGA samples test for?", "options": [ "Dissolved fault gases", "Current", "Colour", "Viscosity only" ], "answer": 0, "explanation": "See MV-515.", "ref": "" }, { "id": "MV504-037", "module": "MV-504", "level": "P", "region": "All", "question": "A planned loading of 75 to 80% in hot climates is used to...", "options": [ "Waste money", "Leave margin for high ambient and peaks", "Avoid testing", "Reduce taps" ], "answer": 1, "explanation": "Hot climates reduce real capacity.", "ref": "" }, { "id": "MV504-038", "module": "MV-504", "level": "E", "region": "All", "question": "Loss load factor from annual load factor LF is often estimated as...", "options": [ "LF²", "1 − LF", "0.3 LF + 0.7 LF²", "LF" ], "answer": 2, "explanation": "Used to estimate annual load losses.", "ref": "" }, { "id": "MV504-039", "module": "MV-504", "level": "P", "region": "All", "question": "Why compare total cost of ownership for transformers?", "options": [ "Taxes", "Paint", "Weight", "Lifetime losses can be similar in value to the purchase price" ], "answer": 3, "explanation": "Capitalise P0 and Pk.", "ref": "" }, { "id": "MV504-040", "module": "MV-504", "level": "B", "region": "All", "question": "What is the HV full-load current of a 1500 kVA transformer at 11 kV?", "options": [ "136 A", "2165 A", "79 A", "52 A" ], "answer": 2, "explanation": "1500/(1.732 × 11).", "ref": "" }, { "id": "MV504-041", "module": "MV-504", "level": "P", "region": "All", "question": "Which typical LV no-load voltage is used in Australia for a 400 V system?", "options": [ "433 V", "380 V", "400 V", "480 V" ], "answer": 0, "explanation": "Allows for voltage drop under load.", "ref": "" }, { "id": "MV504-042", "module": "MV-504", "level": "B", "region": "All", "question": "Which part carries magnetic flux between windings?", "options": [ "Bushing", "Fins", "Tank", "Core" ], "answer": 3, "explanation": "Grain-oriented electrical steel laminations.", "ref": "" }, { "id": "MV504-043", "module": "MV-504", "level": "P", "region": "All", "question": "What do corrugated tank walls replace on sealed transformers?", "options": [ "The core", "Bushings", "The conservator", "The windings" ], "answer": 2, "explanation": "They flex with oil expansion.", "ref": "" }, { "id": "MV504-044", "module": "MV-504", "level": "E", "region": "All", "question": "An LV phase-to-phase fault on a Dyn11 transformer appears on the HV side as...", "options": [ "Zero current", "Earth fault", "Overvoltage", "1.15 times the equivalent 3-phase current in one phase" ], "answer": 3, "explanation": "Delta-star transformation effect.", "ref": "" }, { "id": "MV504-045", "module": "MV-504", "level": "E", "region": "All", "question": "LV earth faults on a Dyn11 transformer are seen by HV earth fault relays...", "options": [ "Not at all, since zero sequence is trapped in the delta", "Only at night", "Twice", "Clearly" ], "answer": 0, "explanation": "Use REF on the LV side.", "ref": "" }, { "id": "MV504-046", "module": "MV-504", "level": "B", "region": "All", "question": "What is a typical largest unit size in GCC building substations?", "options": [ "50 MVA", "100 kVA", "1000 to 2000 kVA", "10 MVA" ], "answer": 2, "explanation": "Often 1000 or 1500 kVA, set by the utility.", "ref": "" }, { "id": "MV504-047", "module": "MV-504", "level": "P", "region": "All", "question": "Why must transformer room ventilation be checked for cast resin units?", "options": [ "Smell", "Noise only", "Heat from losses must leave the room or the unit overheats", "Light" ], "answer": 2, "explanation": "See MV-505.", "ref": "" }, { "id": "MV504-048", "module": "MV-504", "level": "B", "region": "All", "question": "Which transformer type needs an oil pit?", "options": [ "Neither", "Both", "Cast resin", "Oil-immersed" ], "answer": 3, "explanation": "To contain leaks and fire.", "ref": "" }, { "id": "MV505-001", "module": "MV-505", "level": "B", "region": "All", "question": "Which items are usually found in a building distribution substation room?", "options": [ "An RMU, one or more transformers and the LV main board", "Only a capacitor bank", "Only the LV board", "Only a generator" ], "answer": 0, "explanation": "A typical room holds the MV switchgear, the transformers and the LV main board, with a cable trench.", "ref": "" }, { "id": "MV505-002", "module": "MV-505", "level": "B", "region": "All", "question": "Why is a clear operating aisle needed in front of MV switchgear?", "options": [ "To store spare parts", "So an operator can stand clear and doors or panels can open fully", "To reduce cable length", "To improve ventilation only" ], "answer": 1, "explanation": "The aisle gives safe working space and an escape route.", "ref": "IEC 61936-1" }, { "id": "MV505-003", "module": "MV-505", "level": "B", "region": "All", "question": "What is a typical minimum operating aisle width in front of switchgear under IEC 61936-1?", "options": [ "5 m", "About 0.8 m", "3 m", "0.3 m" ], "answer": 1, "explanation": "IEC 61936-1 gives about 0.8 m, and many utilities ask for 1.0 m or more.", "ref": "IEC 61936-1" }, { "id": "MV505-004", "module": "MV-505", "level": "B", "region": "All", "question": "What usually sets the minimum width of the substation equipment door?", "options": [ "The LV cable size", "The RMU height", "The light fittings", "The largest item that must pass through, usually a transformer" ], "answer": 3, "explanation": "The transformer is normally the widest item to deliver or replace.", "ref": "" }, { "id": "MV505-005", "module": "MV-505", "level": "B", "region": "All", "question": "In a naturally ventilated transformer room, where should the inlet and outlet louvres be?", "options": [ "Both at low level", "Only in the roof", "Inlet low and outlet high", "Both at high level" ], "answer": 2, "explanation": "Warm air rises, so a low inlet and high outlet create a stack effect.", "ref": "" }, { "id": "MV505-006", "module": "MV-505", "level": "B", "region": "All", "question": "In the formula S = 0.18 P / √H, what is P?", "options": [ "Air pressure", "Power factor", "Total transformer losses in kW", "Room area in m²" ], "answer": 2, "explanation": "P is the heat to remove, the no-load plus load losses in kW.", "ref": "" }, { "id": "MV505-007", "module": "MV-505", "level": "B", "region": "All", "question": "In the formula S = 0.18 P / √H, what is H?", "options": [ "Transformer height", "Room height", "Trench depth", "Height between the centres of the inlet and outlet louvres" ], "answer": 3, "explanation": "A taller stack gives more natural airflow, so less louvre area is needed.", "ref": "" }, { "id": "MV505-008", "module": "MV-505", "level": "B", "region": "All", "question": "Why do oil-filled transformers need an oil pit or bund?", "options": [ "To contain oil if the tank leaks or bursts", "To reduce noise", "To cool the oil", "To earth the tank" ], "answer": 0, "explanation": "Containment stops oil spreading, feeding a fire or polluting drains.", "ref": "" }, { "id": "MV505-009", "module": "MV-505", "level": "B", "region": "All", "question": "What is the minimum capacity of an oil containment pit for one transformer?", "options": [ "No minimum", "50% of the oil volume", "The full oil volume of the transformer", "10% of the oil volume" ], "answer": 2, "explanation": "It must hold all the oil, plus any allowance the code asks for rain or fire water.", "ref": "" }, { "id": "MV505-010", "module": "MV-505", "level": "B", "region": "All", "question": "Why are cast resin transformers common in high-rise buildings?", "options": [ "They need no ventilation", "They are always cheaper", "They have no losses", "They contain no oil, so fire risk and containment needs are lower" ], "answer": 3, "explanation": "No flammable liquid means simpler fire protection inside occupied buildings.", "ref": "" }, { "id": "MV505-011", "module": "MV-505", "level": "B", "region": "All", "question": "What decides the depth of an MV cable trench in a substation room?", "options": [ "The minimum bending radius of the MV cables", "The door width", "The lighting level", "The LV board colour" ], "answer": 0, "explanation": "Cables must bend up into the switchgear without going below their bending radius.", "ref": "" }, { "id": "MV505-012", "module": "MV-505", "level": "B", "region": "All", "question": "What is a pad-mount or kiosk substation?", "options": [ "A pole-mounted fuse", "An indoor room in a basement", "A packaged outdoor enclosure holding the MV switchgear, transformer and LV board", "A control room" ], "answer": 2, "explanation": "Kiosks are prefabricated units set on a plinth outdoors.", "ref": "IEC 62271-202" }, { "id": "MV505-013", "module": "MV-505", "level": "B", "region": "All", "question": "Which standard covers prefabricated (kiosk) high-voltage/low-voltage substations?", "options": [ "IEC 60909", "IEEE 80", "IEC 62271-202", "IEC 60255" ], "answer": 2, "explanation": "IEC 62271-202 covers prefabricated substations, including internal arc classification.", "ref": "IEC 62271-202" }, { "id": "MV505-014", "module": "MV-505", "level": "B", "region": "All", "question": "Who usually has the final say on the substation room dimensions for a utility-owned substation?", "options": [ "The utility's standard drawings and the local fire code", "The cable supplier", "The interior designer", "The building tenant" ], "answer": 0, "explanation": "Start from the utility standard room drawing to avoid redesign.", "ref": "" }, { "id": "MV505-015", "module": "MV-505", "level": "B", "region": "All", "question": "Why must the utility have direct access to a building substation?", "options": [ "For deliveries to the building", "So its staff can operate and maintain its equipment at any time", "For billing only", "To use the toilets" ], "answer": 1, "explanation": "Utilities normally need 24 hour access, often from outside the building.", "ref": "" }, { "id": "MV505-016", "module": "MV-505", "level": "B", "region": "All", "question": "What is the main reason for fire-rated walls around an indoor oil-filled transformer room?", "options": [ "To keep dust out", "To stop a transformer fire spreading into the building", "Noise control", "To support the roof" ], "answer": 1, "explanation": "Oil fires are intense, so the room is a separate fire compartment.", "ref": "" }, { "id": "MV505-017", "module": "MV-505", "level": "B", "region": "All", "question": "Roughly what clearance is often kept between a transformer and the walls for cooling and access?", "options": [ "About 0.6 m or more", "None", "5 m", "10 m" ], "answer": 0, "explanation": "Space around the unit allows airflow and maintenance access.", "ref": "" }, { "id": "MV505-018", "module": "MV-505", "level": "B", "region": "All", "question": "Why should substation doors open outwards?", "options": [ "To stop dust", "To save space inside", "Because hinges are cheaper", "So people can escape quickly by pushing in an emergency" ], "answer": 3, "explanation": "Outward opening doors with panic hardware help escape during an arc flash or fire.", "ref": "IEC 61936-1" }, { "id": "MV505-019", "module": "MV-505", "level": "B", "region": "All", "question": "Why should water pipes not run through a substation room?", "options": [ "They block ventilation", "They are ugly", "A leak could drip onto live equipment", "They raise the fault level" ], "answer": 2, "explanation": "Utilities and codes normally prohibit unrelated services in the room.", "ref": "" }, { "id": "MV505-020", "module": "MV-505", "level": "P", "region": "All", "question": "A room has transformer losses of 16 kW and 2.25 m between inlet and outlet louvre centres. What inlet area does S = 0.18 P / √H give?", "options": [ "2.88 m²", "1.92 m²", "0.85 m²", "1.28 m²" ], "answer": 1, "explanation": "S = 0.18 × 16 / 1.5 = 1.92 m², and the outlet is made about 10% larger.", "ref": "" }, { "id": "MV505-021", "module": "MV-505", "level": "P", "region": "All", "question": "If the inlet to outlet height is made four times larger, the required louvre area becomes...", "options": [ "Twice as large", "A quarter as large", "Four times larger", "Half as large" ], "answer": 3, "explanation": "S is proportional to 1/√H, and 1/√4 = 0.5.", "ref": "" }, { "id": "MV505-022", "module": "MV-505", "level": "P", "region": "All", "question": "With natural ventilation, how is the outlet louvre usually sized relative to the inlet?", "options": [ "Half the size", "About 10% larger", "Exactly equal always", "Ten times larger" ], "answer": 1, "explanation": "The outlet is made about 10% larger because warm air has expanded.", "ref": "" }, { "id": "MV505-023", "module": "MV-505", "level": "P", "region": "All", "question": "Using Q = P / (1.2 × 1.005 × ΔT), what airflow removes 20 kW with a 10 K air temperature rise?", "options": [ "2.4 m³/s", "1.66 m³/s", "0.6 m³/s", "1.0 m³/s" ], "answer": 1, "explanation": "Q = 20 / (1.2 × 1.005 × 10) = 1.66 m³/s.", "ref": "" }, { "id": "MV505-024", "module": "MV-505", "level": "P", "region": "All", "question": "A bund under a transformer measures 2.5 m by 2.0 m and must hold 1,200 litres of oil. What is the minimum depth?", "options": [ "0.48 m", "0.12 m", "0.24 m", "0.60 m" ], "answer": 2, "explanation": "Volume 1.2 m³ divided by 5 m² gives 0.24 m, before any rain or fire water allowance.", "ref": "" }, { "id": "MV505-025", "module": "MV-505", "level": "P", "region": "All", "question": "An MV cable is 40 mm in diameter and needs a bending radius of 15 times its diameter. What is the minimum bending radius?", "options": [ "400 mm", "600 mm", "150 mm", "1,500 mm" ], "answer": 1, "explanation": "15 × 40 mm = 600 mm, which drives the trench depth below the switchgear.", "ref": "" }, { "id": "MV505-026", "module": "MV-505", "level": "P", "region": "All", "question": "Which losses should be used for P when sizing transformer room ventilation?", "options": [ "No-load losses only", "No-load plus full load losses of all transformers in the room", "LV board losses only", "Load losses only" ], "answer": 1, "explanation": "All heat sources in the room add up, and LV boards in the same room add a little more.", "ref": "" }, { "id": "MV505-027", "module": "MV-505", "level": "P", "region": "All", "question": "Why do utilities ask for a separate LV room in some building substations?", "options": [ "To reduce the MV fault level", "To separate utility-owned MV equipment from customer-operated LV equipment", "To avoid earthing", "To lower the transformer losses" ], "answer": 1, "explanation": "Separation lets each party operate and lock its own equipment safely.", "ref": "" }, { "id": "MV505-028", "module": "MV-505", "level": "P", "region": "All", "question": "What does an internal arc classification such as IAC AFL on a kiosk tell you?", "options": [ "Its IP rating", "Which sides are tested as safe for people during an internal arc", "Its fault level only", "Its colour" ], "answer": 1, "explanation": "A, F, L and R give accessibility and the front, lateral and rear sides tested.", "ref": "IEC 62271-202" }, { "id": "MV505-029", "module": "MV-505", "level": "P", "region": "All", "question": "Why is a pressure relief path important for indoor MV switchgear rooms?", "options": [ "To lower noise", "To cool the room", "To keep dust out", "To vent hot arc gases safely away from operators and the building" ], "answer": 3, "explanation": "Internal arc gases must be ducted or vented so the room and people are protected.", "ref": "IEC 62271-200" }, { "id": "MV505-030", "module": "MV-505", "level": "P", "region": "All", "question": "What is a common way to stop oil from a bund draining into the stormwater system?", "options": [ "Use larger pipes", "Leave it open", "Use an oil separator or an interceptor before discharge", "Pump it to the sewer" ], "answer": 2, "explanation": "Separators hold oil while allowing clean rainwater to drain.", "ref": "" }, { "id": "MV505-031", "module": "MV-505", "level": "P", "region": "All", "question": "Why is a sump or drain with a fire trap (such as a pebble layer) used in oil pits?", "options": [ "To cool the transformer", "To reduce noise", "To quench burning oil as it drains into the pit", "To improve earthing" ], "answer": 2, "explanation": "A layer of stones or a flame trap helps extinguish burning oil.", "ref": "" }, { "id": "MV505-032", "module": "MV-505", "level": "P", "region": "All", "question": "When laying out two transformers side by side, what must be kept in mind for maintenance?", "options": [ "Nothing", "Clear space to remove or skate one unit out without moving the other", "They must face opposite walls", "They must touch" ], "answer": 1, "explanation": "Each transformer should be replaceable independently along a clear route.", "ref": "" }, { "id": "MV505-033", "module": "MV-505", "level": "P", "region": "All", "question": "Why do cable entries into a substation need sealing?", "options": [ "To stop water, gas, vermin and fire spreading through the openings", "For appearance", "To reduce cable size", "To raise the fault level" ], "answer": 0, "explanation": "Entry seals keep out water and pests and maintain fire separation.", "ref": "" }, { "id": "MV505-034", "module": "MV-505", "level": "P", "region": "All", "question": "Why do outdoor kiosks need clearances from buildings, windows and boundaries?", "options": [ "To limit fire spread and allow access and cooling", "For metering", "For appearance", "To raise voltage" ], "answer": 0, "explanation": "Fire separation and access clearances come from the substation code and utility rules.", "ref": "" }, { "id": "MV505-035", "module": "MV-505", "level": "E", "region": "All", "question": "For forced ventilation removing 15 kW with a 12 K air temperature rise, what is the airflow from Q = P / (1.2 × 1.005 × ΔT)?", "options": [ "3.1 m³/s", "0.52 m³/s", "1.04 m³/s", "2.08 m³/s" ], "answer": 2, "explanation": "Q = 15 / (1.2 × 1.005 × 12) = 1.04 m³/s.", "ref": "" }, { "id": "MV505-036", "module": "MV-505", "level": "E", "region": "All", "question": "A room inlet louvre is sized for 16 kW losses. The losses rise to 24 kW with H unchanged. By how much must the inlet area change?", "options": [ "2.25 times", "About 1.22 times", "1.5 times", "It stays the same" ], "answer": 2, "explanation": "S is directly proportional to P, so 24/16 = 1.5 times.", "ref": "" }, { "id": "MV505-037", "module": "MV-505", "level": "E", "region": "All", "question": "Why does the effective free area of a louvre matter more than its face size?", "options": [ "It does not", "Free area is always larger", "Blades, mesh and sand traps can cut the free area to around half the face area", "It only affects noise" ], "answer": 2, "explanation": "Ventilation formulas give free area, so the face area must be larger to suit the louvre type.", "ref": "" }, { "id": "MV505-038", "module": "MV-505", "level": "E", "region": "All", "question": "Why should a transformer room be checked for the hottest design day rather than average ambient?", "options": [ "Ambient has no effect", "It only affects LV boards", "Transformers run cooler in summer", "Transformer rating assumes limits on ambient air temperature, so hot inlet air reduces the margin" ], "answer": 3, "explanation": "IEC 60076-2 ratings assume average and maximum ambient limits, and hot rooms need derating or more cooling.", "ref": "IEC 60076-2" }, { "id": "MV505-039", "module": "MV-505", "level": "E", "region": "All", "question": "Two oil-filled transformers share one bund. How should the bund be sized as a minimum?", "options": [ "For the oil of the largest single transformer, unless the code asks for more", "For 10% of total oil", "For the smaller unit", "No bund is needed" ], "answer": 0, "explanation": "A common basis is the largest single unit, but some codes ask for more allowance, so check locally.", "ref": "" }, { "id": "MV505-040", "module": "MV-505", "level": "E", "region": "All", "question": "What is the main purpose of a fire separation wall between two outdoor oil-filled transformers?", "options": [ "To earth the tanks", "To stop a fire in one unit damaging the other", "To support cables", "To reduce noise" ], "answer": 1, "explanation": "Where spacing is too small, a fire wall protects the adjacent unit.", "ref": "IEC 61936-1" }, { "id": "MV505-041", "module": "MV-505", "level": "E", "region": "All", "question": "Why can a basement substation need extra protection against flooding?", "options": [ "It improves earthing", "Water ingress can reach live equipment and cable entries", "Basements are cooler", "It is required for ventilation" ], "answer": 1, "explanation": "Raised plinths, sealed entries and sump pumps reduce flood risk.", "ref": "" }, { "id": "MV505-042", "module": "MV-505", "level": "B", "region": "GCC", "question": "Why do GCC substation rooms often use sand-trap louvres?", "options": [ "To stop windblown sand and dust entering with the cooling air", "For appearance", "To reduce noise", "To raise air pressure" ], "answer": 0, "explanation": "Dust builds up on insulation and cooling surfaces.", "ref": "" }, { "id": "MV505-043", "module": "MV-505", "level": "P", "region": "GCC", "question": "Why are fans often needed in GCC transformer rooms even when natural ventilation is possible elsewhere?", "options": [ "Humidity is always low", "Dust only", "Outside air at 45 to 50 °C leaves little temperature headroom", "Rules ban louvres" ], "answer": 2, "explanation": "Hot inlet air means more airflow is needed to remove the same heat.", "ref": "" }, { "id": "MV505-044", "module": "MV-505", "level": "B", "region": "GCC", "question": "In a typical Dubai building substation, who usually owns the RMU and transformers?", "options": [ "The tenant", "The building owner", "The utility (DEWA)", "The contractor" ], "answer": 2, "explanation": "The utility owns the MV equipment and transformers, while the building owns the LV board.", "ref": "" }, { "id": "MV505-045", "module": "MV-505", "level": "P", "region": "GCC", "question": "Which authority's rules govern fire separation of a substation room in a Dubai building alongside DEWA requirements?", "options": [ "RTA", "Dubai Municipality planning only", "Dubai Civil Defence", "The tenant" ], "answer": 2, "explanation": "Fire separation, detection and suppression follow the UAE Fire and Life Safety Code enforced by Civil Defence.", "ref": "" }, { "id": "MV505-046", "module": "MV-505", "level": "B", "region": "AU", "question": "Which Australian standard covers substation design, clearances and oil containment?", "options": [ "AS 2067", "AS 3008", "AS/NZS 3000", "AS 1170" ], "answer": 0, "explanation": "AS 2067 covers substations and high voltage installations.", "ref": "AS 2067" }, { "id": "MV505-047", "module": "MV-505", "level": "P", "region": "AU", "question": "Which type of distribution substation is very common in Australian residential subdivisions?", "options": [ "Pad-mount kiosks", "Underground vaults only", "Pole-top only", "Indoor basement rooms" ], "answer": 0, "explanation": "Pad-mount kiosks are widely used for underground residential networks.", "ref": "" }, { "id": "MV505-048", "module": "MV-505", "level": "P", "region": "NZ", "question": "Which New Zealand standards cover seismic design of substation plinths and equipment restraint?", "options": [ "AS 2067 only", "IEC 60909", "NZS 3604 only", "NZS 1170.5 and NZS 4219" ], "answer": 3, "explanation": "NZS 1170.5 sets earthquake actions and NZS 4219 covers restraint of engineering systems.", "ref": "NZS 4219" }, { "id": "MV505-049", "module": "MV-505", "level": "B", "region": "NZ", "question": "In New Zealand, who usually sets the kiosk and substation room standards for a connection?", "options": [ "The council only", "WorkSafe", "Transpower", "The local lines company" ], "answer": 3, "explanation": "Lines companies such as Vector and Orion publish their own standards.", "ref": "" }, { "id": "MV505-050", "module": "MV-505", "level": "B", "region": "Asia", "question": "Which utility publishes substation room requirements for consumers in Singapore?", "options": [ "DEWA", "TNB", "SP Group", "Ausgrid" ], "answer": 2, "explanation": "SP Group sets room sizes and layouts for each transformer arrangement.", "ref": "" }, { "id": "MV505-051", "module": "MV-505", "level": "P", "region": "Asia", "question": "Which utility sets consumer substation room requirements in Peninsular Malaysia?", "options": [ "KAHRAMAA", "SP Group", "Vector", "TNB" ], "answer": 3, "explanation": "Tenaga Nasional Berhad publishes its substation requirements.", "ref": "" }, { "id": "MV506-001", "module": "MV-506", "level": "B", "region": "All", "question": "What does IEC 60909 calculate?", "options": [ "Short-circuit currents in three-phase AC systems", "Lighting levels", "Cable ampacity", "Earth grid resistance" ], "answer": 0, "explanation": "IEC 60909-0 is the standard method for short-circuit currents.", "ref": "IEC 60909-0" }, { "id": "MV506-002", "module": "MV-506", "level": "B", "region": "All", "question": "In IEC 60909, what replaces all the sources in the network?", "options": [ "One equivalent voltage source c·Un/√3 at the fault point", "A capacitor", "A current source at each generator", "Nothing" ], "answer": 0, "explanation": "All other sources are shorted and one voltage source is placed at the fault.", "ref": "IEC 60909-0" }, { "id": "MV506-003", "module": "MV-506", "level": "B", "region": "All", "question": "What is the IEC 60909 voltage factor cmax for maximum MV fault currents?", "options": [ "0.95", "1.00", "1.10", "1.05" ], "answer": 2, "explanation": "cmax = 1.10 for MV systems.", "ref": "IEC 60909-0" }, { "id": "MV506-004", "module": "MV-506", "level": "B", "region": "All", "question": "Why is the c factor used?", "options": [ "To convert kA to MVA", "To cover the real operating voltage being higher or lower than nominal", "To account for motor slip", "To include cable temperature" ], "answer": 1, "explanation": "c scales the nominal voltage to the highest or lowest likely operating voltage.", "ref": "IEC 60909-0" }, { "id": "MV506-005", "module": "MV-506", "level": "B", "region": "All", "question": "What is the fault level in MVA of an 11 kV system with a 25 kA three-phase fault current?", "options": [ "550 MVA", "476 MVA", "825 MVA", "275 MVA" ], "answer": 1, "explanation": "S = √3 × 11 × 25 = 476 MVA.", "ref": "" }, { "id": "MV506-006", "module": "MV-506", "level": "B", "region": "All", "question": "What is the three-phase fault current of an 11 kV system with a 250 MVA fault level?", "options": [ "13.1 kA", "9.1 kA", "25 kA", "22.7 kA" ], "answer": 0, "explanation": "I = 250 / (√3 × 11) = 13.1 kA.", "ref": "" }, { "id": "MV506-007", "module": "MV-506", "level": "B", "region": "All", "question": "What usually limits the fault level at a transformer's LV terminals the most?", "options": [ "The breaker", "The MV cable", "The LV busbar", "The transformer impedance" ], "answer": 3, "explanation": "Transformer impedance is much larger than the MV source impedance referred to LV.", "ref": "" }, { "id": "MV506-008", "module": "MV-506", "level": "B", "region": "All", "question": "Using Ik ≈ In / uk with an infinite source, what is the LV fault level of a 1500 kVA, 6% transformer at 400 V?", "options": [ "28.9 kA", "21.7 kA", "48.1 kA", "36.1 kA" ], "answer": 3, "explanation": "In = 2,165 A and 2,165 / 0.06 = 36.1 kA.", "ref": "" }, { "id": "MV506-009", "module": "MV-506", "level": "B", "region": "All", "question": "What does a higher transformer impedance (uk %) do to the LV fault level?", "options": [ "Raises it", "Lowers it", "No change", "Doubles it" ], "answer": 1, "explanation": "Fault current is inversely proportional to impedance.", "ref": "" }, { "id": "MV506-010", "module": "MV-506", "level": "B", "region": "All", "question": "What happens to the fault level as you move further from the transformer along a cable?", "options": [ "It rises", "It doubles", "It falls because cable impedance adds up", "It stays the same" ], "answer": 2, "explanation": "Every metre of cable or busduct adds impedance.", "ref": "" }, { "id": "MV506-011", "module": "MV-506", "level": "B", "region": "All", "question": "What does Icu mean on an LV circuit breaker?", "options": [ "Earth fault current", "Short-time withstand current", "Rated current", "Rated ultimate short-circuit breaking capacity" ], "answer": 3, "explanation": "Icu is the highest fault current the breaker can interrupt, though it may not be fit for further service.", "ref": "IEC 60947-2" }, { "id": "MV506-012", "module": "MV-506", "level": "B", "region": "All", "question": "What does Ics mean on an LV circuit breaker?", "options": [ "Thermal current", "Service short-circuit breaking capacity after which the breaker remains usable", "Instantaneous setting", "Making current" ], "answer": 1, "explanation": "Ics is stated as 25, 50, 75 or 100% of Icu.", "ref": "IEC 60947-2" }, { "id": "MV506-013", "module": "MV-506", "level": "B", "region": "All", "question": "What does Icw describe?", "options": [ "The cable rating", "The short-time current a device can carry for a set time, often 1 s", "The inrush current", "The current a device can break" ], "answer": 1, "explanation": "Icw lets an ACB or board carry the fault while downstream devices clear it.", "ref": "IEC 60947-2" }, { "id": "MV506-014", "module": "MV-506", "level": "B", "region": "All", "question": "Why must breakers have a making capacity above the peak fault current?", "options": [ "To allow closing onto a fault without damage", "To set the TMS", "To reduce losses", "To limit voltage" ], "answer": 0, "explanation": "Closing onto a fault meets the first asymmetrical peak.", "ref": "" }, { "id": "MV506-015", "module": "MV-506", "level": "B", "region": "All", "question": "Do running induction motors contribute to a nearby fault?", "options": [ "Only when stopped", "Yes, for the first few cycles", "Only DC motors", "No, never" ], "answer": 1, "explanation": "Motors act briefly as generators, roughly at their locked-rotor current, then decay.", "ref": "IEC 60909-0" }, { "id": "MV506-016", "module": "MV-506", "level": "B", "region": "All", "question": "What does a load flow study mainly calculate?", "options": [ "Bus voltages, branch currents and losses under normal load", "Insulation resistance", "Lighting levels", "Earth resistance" ], "answer": 0, "explanation": "Load flow checks voltage limits and equipment loading in steady state.", "ref": "" }, { "id": "MV506-017", "module": "MV-506", "level": "B", "region": "All", "question": "What usually causes most of the voltage drop in a building supply at full load?", "options": [ "The transformer and long LV cables", "The ACB", "The busbar joints", "The MV cable" ], "answer": 0, "explanation": "Transformer impedance and long, small LV cables dominate.", "ref": "" }, { "id": "MV506-018", "module": "MV-506", "level": "B", "region": "All", "question": "Raising an off-circuit tap by one step on a distribution transformer typically changes the LV voltage by about...", "options": [ "0.5%", "25%", "2.5%", "10%" ], "answer": 2, "explanation": "Off-circuit taps are usually in 2.5% steps.", "ref": "" }, { "id": "MV506-019", "module": "MV-506", "level": "B", "region": "All", "question": "What is cmin for minimum fault currents at LV in IEC 60909?", "options": [ "1.10", "1.05", "0.95", "1.00" ], "answer": 2, "explanation": "Minimum currents are used to check protection sensitivity.", "ref": "IEC 60909-0" }, { "id": "MV506-020", "module": "MV-506", "level": "P", "region": "All", "question": "Using Ik ≈ In / uk with an infinite source, what is the LV fault level of a 2000 kVA, 6% transformer at 400 V?", "options": [ "42.0 kA", "48.1 kA", "57.7 kA", "36.1 kA" ], "answer": 1, "explanation": "In = 2,887 A and 2,887 / 0.06 = 48.1 kA.", "ref": "" }, { "id": "MV506-021", "module": "MV-506", "level": "P", "region": "All", "question": "Using Ik ≈ In / uk with an infinite source, what is the LV fault level of a 2500 kVA, 6.25% transformer at 400 V?", "options": [ "57.7 kA", "65.0 kA", "45.2 kA", "50.0 kA" ], "answer": 0, "explanation": "In = 3,608 A and 3,608 / 0.0625 = 57.7 kA.", "ref": "" }, { "id": "MV506-022", "module": "MV-506", "level": "P", "region": "All", "question": "What is the source impedance at 11 kV from a 250 MVA fault level using Zq = c·Un² / S\"k with c = 1.1?", "options": [ "0.048 Ω", "5.3 Ω", "0.53 Ω", "0.48 Ω" ], "answer": 2, "explanation": "Zq = 1.1 × 11² / 250 = 0.532 Ω.", "ref": "IEC 60909-0" }, { "id": "MV506-023", "module": "MV-506", "level": "P", "region": "All", "question": "What is the impedance in ohms, referred to 400 V, of a 1500 kVA, 6% transformer?", "options": [ "0.64 Ω", "0.0016 Ω", "0.064 Ω", "0.0064 Ω" ], "answer": 3, "explanation": "Z = uk × U² / S = 0.06 × 0.4² / 1.5 = 0.0064 Ω.", "ref": "" }, { "id": "MV506-024", "module": "MV-506", "level": "P", "region": "All", "question": "A 1.5 MVA transformer has 6% impedance. What is its impedance on a 100 MVA base?", "options": [ "6.0 pu", "0.6 pu", "0.09 pu", "4.0 pu" ], "answer": 3, "explanation": "Z = 0.06 × 100 / 1.5 = 4.0 pu.", "ref": "" }, { "id": "MV506-025", "module": "MV-506", "level": "P", "region": "All", "question": "A 1.5 MVA, 6% transformer is fed from a 250 MVA source. Ignoring the c factor, roughly what is the LV fault current at 400 V?", "options": [ "22.7 kA", "32.8 kA", "40.5 kA", "36.1 kA" ], "answer": 1, "explanation": "Transformer fault MVA is 25. Combined: 1/(1/250 + 1/25) = 22.7 MVA, and 22.7 / (√3 × 0.4) = 32.8 kA.", "ref": "" }, { "id": "MV506-026", "module": "MV-506", "level": "P", "region": "All", "question": "What does κ in ip = κ·√2·Ik\" account for?", "options": [ "The DC offset that raises the first peak", "Earth resistance", "Cable temperature", "Motor slip" ], "answer": 0, "explanation": "κ depends on R/X and sits between 1.02 and 2.0.", "ref": "IEC 60909-0" }, { "id": "MV506-027", "module": "MV-506", "level": "P", "region": "All", "question": "Using κ = 1.02 + 0.98e^(−3R/X), what is κ for R/X = 0.1?", "options": [ "1.95", "1.61", "1.75", "1.42" ], "answer": 2, "explanation": "κ = 1.02 + 0.98 × e^(−0.3) = 1.02 + 0.98 × 0.741 = 1.75.", "ref": "IEC 60909-0" }, { "id": "MV506-028", "module": "MV-506", "level": "P", "region": "All", "question": "What happens to κ as the X/R ratio increases?", "options": [ "It falls toward 1", "It rises toward 2", "It stays at 1.41", "It becomes negative" ], "answer": 1, "explanation": "High X/R means the DC offset decays slowly, so the peak is higher.", "ref": "" }, { "id": "MV506-029", "module": "MV-506", "level": "P", "region": "All", "question": "Roughly what is a line-to-line fault current compared with the three-phase fault current, far from generators?", "options": [ "About 2 times", "About 0.5 times", "About 1.15 times", "About 0.87 times" ], "answer": 3, "explanation": "Ik2 = (√3/2) × Ik3 when positive and negative sequence impedances are equal.", "ref": "IEC 60909-0" }, { "id": "MV506-030", "module": "MV-506", "level": "P", "region": "All", "question": "Why can an LV earth fault at the terminals of a Dyn11 transformer be slightly higher than the three-phase fault?", "options": [ "Cables are shorter", "Motors add more current", "The delta winding gives a low zero-sequence impedance", "The c factor is higher for earth faults" ], "answer": 2, "explanation": "With Z0 close to Z1 at the transformer, the single-phase fault can match or exceed Ik3.", "ref": "" }, { "id": "MV506-031", "module": "MV-506", "level": "P", "region": "All", "question": "Which fault current is used to check that protection operates for automatic disconnection at the end of a circuit?", "options": [ "Maximum three-phase fault", "Peak current", "Minimum earth fault current", "Motor starting current" ], "answer": 2, "explanation": "The lowest earth fault current must still trip the device in the required time.", "ref": "" }, { "id": "MV506-032", "module": "MV-506", "level": "P", "region": "All", "question": "What is the voltage drop on a three-phase circuit of 100 m at 200 A, using a cable with 0.4 mV/A/m?", "options": [ "16 V (4%)", "8 V (2%)", "40 V (10%)", "4 V (1%)" ], "answer": 1, "explanation": "0.4 × 200 × 100 / 1000 = 8 V, which is 2% of 400 V.", "ref": "" }, { "id": "MV506-033", "module": "MV-506", "level": "P", "region": "All", "question": "An LV breaker has Icu = 50 kA and Ics = 75%. What is its service breaking capacity?", "options": [ "37.5 kA", "75 kA", "25 kA", "50 kA" ], "answer": 0, "explanation": "Ics = 0.75 × 50 = 37.5 kA.", "ref": "IEC 60947-2" }, { "id": "MV506-034", "module": "MV-506", "level": "P", "region": "All", "question": "A board must carry fault current while downstream breakers clear with a short-time delay. Which rating is most relevant?", "options": [ "In", "Ir", "Icu", "Icw" ], "answer": 3, "explanation": "Icw is the short-time withstand, used for selective (delayed) incomers.", "ref": "IEC 61439-1" }, { "id": "MV506-035", "module": "MV-506", "level": "P", "region": "All", "question": "Roughly how much fault current does a running induction motor contribute at its terminals initially?", "options": [ "Zero", "100 times full load", "About its full load current", "About its locked-rotor current, often 5 to 7 times full load" ], "answer": 3, "explanation": "The initial contribution is close to the starting current and decays within a few cycles.", "ref": "" }, { "id": "MV506-036", "module": "MV-506", "level": "E", "region": "All", "question": "Using κ = 1.02 + 0.98e^(−3R/X), what is the peak current for Ik\" = 30 kA with R/X = 0.1?", "options": [ "84.9 kA", "42.4 kA", "74.1 kA", "52.4 kA" ], "answer": 2, "explanation": "κ = 1.746, so ip = 1.746 × √2 × 30 = 74.1 kA.", "ref": "IEC 60909-0" }, { "id": "MV506-037", "module": "MV-506", "level": "E", "region": "All", "question": "What is κ for an X/R ratio of 14?", "options": [ "1.66", "1.81", "1.51", "1.98" ], "answer": 1, "explanation": "R/X = 0.0714, so κ = 1.02 + 0.98 × e^(−0.214) = 1.81.", "ref": "IEC 60909-0" }, { "id": "MV506-038", "module": "MV-506", "level": "E", "region": "All", "question": "Under IEC 60947-2, what minimum ratio of making capacity to Icu applies for a breaker with Icu between 20 and 50 kA at cos φ 0.25?", "options": [ "2.0", "1.7", "2.1", "2.2" ], "answer": 2, "explanation": "n = 2.1 for 20 < I ≤ 50 kA, so a 50 kA breaker needs at least 105 kA making capacity.", "ref": "IEC 60947-2" }, { "id": "MV506-039", "module": "MV-506", "level": "E", "region": "All", "question": "What does the IEC 60909 impedance correction factor KT do?", "options": [ "Corrects cable temperature", "Sets the c factor", "Adjusts network transformer impedance so results match real operating conditions", "Adds motor contribution" ], "answer": 2, "explanation": "KT = 0.95·cmax / (1 + 0.6·xT) is applied to network transformer impedances.", "ref": "IEC 60909-0" }, { "id": "MV506-040", "module": "MV-506", "level": "E", "region": "All", "question": "For maximum fault currents, at what temperature does IEC 60909 take cable resistance?", "options": [ "70 °C", "90 °C", "20 °C", "250 °C" ], "answer": 2, "explanation": "Lower resistance at 20 °C gives the highest currents. Minimum currents use the end-of-fault temperature.", "ref": "IEC 60909-0" }, { "id": "MV506-041", "module": "MV-506", "level": "E", "region": "All", "question": "In IEC 60909, what is the formula for the single-phase-to-earth initial fault current?", "options": [ "c·Un/(2·Z1)", "c·Un·Z0", "√3·c·Un / |Z1 + Z2 + Z0|", "c·Un/(√3·Z1)" ], "answer": 2, "explanation": "Ik1\" = √3·c·Un / |Z(1) + Z(2) + Z(0)|.", "ref": "IEC 60909-0" }, { "id": "MV506-042", "module": "MV-506", "level": "E", "region": "All", "question": "Why does a far-from-generator fault in IEC 60909 let you take Ib (breaking current) equal to Ik\"?", "options": [ "Because c = 1", "Because AC components do not decay when generators are electrically far away", "Because R/X is zero", "Because motors are ignored" ], "answer": 1, "explanation": "With no significant AC decay, Ik\" = Ib = Ik.", "ref": "IEC 60909-0" }, { "id": "MV506-043", "module": "MV-506", "level": "E", "region": "All", "question": "In a load flow, why might a lightly loaded long MV cable network see voltage rise rather than drop?", "options": [ "Transformers boost it", "Motors raise it", "The c factor applies", "Cable charging current (capacitance) produces reactive power that lifts voltage" ], "answer": 3, "explanation": "Cable capacitance generates reactive power that can raise voltage at light load.", "ref": "" }, { "id": "MV506-044", "module": "MV-506", "level": "E", "region": "All", "question": "Why must fault level studies include future network changes from the utility?", "options": [ "They never change", "Only for lighting", "For billing", "Utility upgrades can raise the MV fault level above the equipment rating" ], "answer": 3, "explanation": "Equipment should be rated for the utility's declared design fault level, not today's value.", "ref": "" }, { "id": "MV506-045", "module": "MV-506", "level": "B", "region": "GCC", "question": "What is a typical design 11 kV fault level declared by GCC utilities for distribution equipment?", "options": [ "5 kA", "20 to 31.5 kA", "2 kA", "100 kA" ], "answer": 1, "explanation": "Utilities declare values such as 20, 25 or 31.5 kA at 11 kV.", "ref": "" }, { "id": "MV506-046", "module": "MV-506", "level": "P", "region": "GCC", "question": "Why are LV main boards in GCC buildings often specified at 50 to 65 kA?", "options": [ "Large transformers such as 1500 to 2000 kVA give LV fault levels near or above 36 to 48 kA", "To reduce cost", "They are required for lighting", "To lower voltage drop" ], "answer": 0, "explanation": "Transformer size and impedance push LV fault levels high, so boards need high ratings.", "ref": "" }, { "id": "MV506-047", "module": "MV-506", "level": "P", "region": "KSA", "question": "Which MV distribution voltage is widely used for short-circuit studies in Saudi cities?", "options": [ "11 kV", "22 kV", "13.8 kV", "66 kV" ], "answer": 2, "explanation": "SEC uses 13.8 kV widely, with 33 kV also in use, at 60 Hz.", "ref": "" }, { "id": "MV506-048", "module": "MV-506", "level": "B", "region": "AU", "question": "In Australia and New Zealand, which standard requires the prospective fault current at the main switchboard to be determined?", "options": [ "AS 1940", "IEEE 80", "AS 2067", "AS/NZS 3000" ], "answer": 3, "explanation": "AS/NZS 3000 Wiring Rules require the fault level to be known for equipment selection.", "ref": "AS/NZS 3000" }, { "id": "MV506-049", "module": "MV-506", "level": "P", "region": "NZ", "question": "Which standard is commonly used in AU and NZ for cable impedance data in fault and voltage drop calculations?", "options": [ "NZS 4219", "AS/NZS 3008.1", "IEC 60287 only", "IEEE 80" ], "answer": 1, "explanation": "AS/NZS 3008.1 gives cable impedances, ratings and voltage drop data.", "ref": "AS/NZS 3008.1" }, { "id": "MV506-050", "module": "MV-506", "level": "B", "region": "Asia", "question": "What do utilities in Asia such as SP Group or TNB usually provide to a consumer for short-circuit design?", "options": [ "Nothing", "The prospective fault level at the point of supply", "The relay TMS of every feeder", "Earth grid drawings" ], "answer": 1, "explanation": "Designers start from the declared fault level at the point of supply.", "ref": "" }, { "id": "MV506-051", "module": "MV-506", "level": "P", "region": "AU", "question": "In Australia, where does a designer usually get the prospective fault current at the point of supply?", "options": [ "From the network operator", "It is always 10 kA", "From AS 2067 tables", "From the cable supplier" ], "answer": 0, "explanation": "Network operators publish or provide the fault level at the connection point.", "ref": "" }, { "id": "MV506-052", "module": "MV-506", "level": "E", "region": "GCC", "question": "A GCC utility declares 31.5 kA at 11 kV. What fault level in MVA is that?", "options": [ "693 MVA", "347 MVA", "600 MVA", "520 MVA" ], "answer": 2, "explanation": "S = √3 × 11 × 31.5 = 600 MVA.", "ref": "" }, { "id": "MV507-001", "module": "MV-507", "level": "B", "region": "All", "question": "What does IDMT stand for?", "options": [ "Instant direct maximum trip", "Internal delay mode timer", "Inverse definite minimum time", "Inverse direct magnetic trip" ], "answer": 2, "explanation": "IDMT relays trip faster as current rises, with a definite minimum time at high currents.", "ref": "IEC 60255-151" }, { "id": "MV507-002", "module": "MV-507", "level": "B", "region": "All", "question": "What does the TMS setting do on an IDMT relay?", "options": [ "Moves the whole curve up or down in time", "Sets the CT ratio", "Changes the curve shape", "Changes the pickup current" ], "answer": 0, "explanation": "TMS scales the operating time at every current.", "ref": "" }, { "id": "MV507-003", "module": "MV-507", "level": "B", "region": "All", "question": "What does the pickup (plug) setting Is set?", "options": [ "The tripping time", "The CT knee-point", "The breaker speed", "The current at which the relay starts timing" ], "answer": 3, "explanation": "Below Is the relay does not operate.", "ref": "" }, { "id": "MV507-004", "module": "MV-507", "level": "B", "region": "All", "question": "What are the IEC standard inverse constants k and α?", "options": [ "k = 13.5, α = 1", "k = 80, α = 2", "k = 120, α = 1", "k = 0.14, α = 0.02" ], "answer": 3, "explanation": "t = TMS × 0.14 / ((I/Is)^0.02 − 1).", "ref": "IEC 60255-151" }, { "id": "MV507-005", "module": "MV-507", "level": "B", "region": "All", "question": "Which IEC curve has k = 13.5 and α = 1?", "options": [ "Standard inverse", "Long time inverse", "Very inverse", "Extremely inverse" ], "answer": 2, "explanation": "Very inverse: t = TMS × 13.5 / ((I/Is) − 1).", "ref": "IEC 60255-151" }, { "id": "MV507-006", "module": "MV-507", "level": "B", "region": "All", "question": "Which IEC curve has k = 80 and α = 2?", "options": [ "Standard inverse", "Long time inverse", "Very inverse", "Extremely inverse" ], "answer": 3, "explanation": "Extremely inverse grades well with fuses.", "ref": "IEC 60255-151" }, { "id": "MV507-007", "module": "MV-507", "level": "B", "region": "All", "question": "What is a typical grading margin between two IDMT relays?", "options": [ "0.01 s", "10 s", "2 s", "0.3 to 0.4 s" ], "answer": 3, "explanation": "It covers breaker opening time, relay overshoot, errors and a safety margin.", "ref": "" }, { "id": "MV507-008", "module": "MV-507", "level": "B", "region": "All", "question": "What does discrimination (selectivity) mean?", "options": [ "The upstream breaker trips first", "All breakers trip together", "Fuses never blow", "Only the device nearest the fault trips" ], "answer": 3, "explanation": "Good selectivity keeps the rest of the network on supply.", "ref": "" }, { "id": "MV507-009", "module": "MV-507", "level": "B", "region": "All", "question": "What is ANSI device number 50?", "options": [ "Time overcurrent", "Undervoltage", "Differential", "Instantaneous overcurrent" ], "answer": 3, "explanation": "50 is instantaneous, 51 is time-delayed overcurrent.", "ref": "" }, { "id": "MV507-010", "module": "MV-507", "level": "B", "region": "All", "question": "What is ANSI device number 87?", "options": [ "Lockout", "Distance", "Directional overcurrent", "Differential" ], "answer": 3, "explanation": "Differential protection compares currents into and out of a zone.", "ref": "" }, { "id": "MV507-011", "module": "MV-507", "level": "B", "region": "All", "question": "What is ANSI device number 67?", "options": [ "Earth fault", "Directional overcurrent", "Breaker failure", "Frequency" ], "answer": 1, "explanation": "67 trips only for fault current flowing in a set direction.", "ref": "" }, { "id": "MV507-012", "module": "MV-507", "level": "B", "region": "All", "question": "What does magnetising inrush mean for transformer protection?", "options": [ "A large short current when energising that must not cause a trip", "A loss of earth", "Overvoltage", "A fault inside the transformer" ], "answer": 0, "explanation": "Inrush can be about 12 times rated current for around 0.1 s.", "ref": "" }, { "id": "MV507-013", "module": "MV-507", "level": "B", "region": "All", "question": "What does 5P20 mean on a protection CT?", "options": [ "5 A secondary, 20 VA", "5 cores and 20 turns", "5% composite error at 20 times rated current", "Class 5 at 20 °C" ], "answer": 2, "explanation": "The CT stays within 5% composite error up to 20 times rated current at rated burden.", "ref": "IEC 61869-2" }, { "id": "MV507-014", "module": "MV-507", "level": "B", "region": "All", "question": "What happens if a protection CT saturates during a fault?", "options": [ "Nothing", "The relay sees less current and may trip late or not at all", "The relay trips faster", "The voltage rises" ], "answer": 1, "explanation": "A saturated CT cannot reproduce the primary current.", "ref": "" }, { "id": "MV507-015", "module": "MV-507", "level": "B", "region": "All", "question": "What do the letters L, S, I and G mean on an ACB trip unit?", "options": [ "Long time, Short time, Instantaneous, Ground fault", "Load, Supply, Isolate, Generate", "Line, Star, Insulation, Grid", "Low, Slow, Instant, Ground" ], "answer": 0, "explanation": "Each function covers a different part of the time-current curve.", "ref": "IEC 60947-2" }, { "id": "MV507-016", "module": "MV-507", "level": "B", "region": "All", "question": "Why is an HV fuse often less selective with the LV main ACB than a relay and CB?", "options": [ "The fuse can melt before the ACB short-time delay ends", "ACBs are always slow", "Fuses never blow", "Fuses work only at LV" ], "answer": 0, "explanation": "High LV fault currents melt the HV fuse in tens of milliseconds.", "ref": "" }, { "id": "MV507-017", "module": "MV-507", "level": "B", "region": "All", "question": "What does restricted earth fault (REF) protection detect?", "options": [ "Earth faults within the protected transformer winding zone", "Phase-to-phase faults on LV cables", "Low frequency", "Overloads" ], "answer": 0, "explanation": "REF is sensitive to winding earth faults but stable for faults outside its zone.", "ref": "" }, { "id": "MV507-018", "module": "MV-507", "level": "B", "region": "All", "question": "What does a core balance CT measure?", "options": [ "The residual (earth leakage) current as all phase conductors pass through it", "Voltage", "Frequency", "Phase current only" ], "answer": 0, "explanation": "Healthy load currents cancel, so only earth fault current is seen.", "ref": "" }, { "id": "MV507-019", "module": "MV-507", "level": "B", "region": "All", "question": "Why must protection curves stay below the transformer damage curve?", "options": [ "For metering", "To clear through faults before the transformer is thermally or mechanically damaged", "To trip on inrush", "To reduce losses" ], "answer": 1, "explanation": "The damage curve shows how long the transformer can withstand fault current.", "ref": "IEEE C57.109" }, { "id": "MV507-020", "module": "MV-507", "level": "P", "region": "All", "question": "Using the IEC standard inverse curve, what is the trip time at 10 times Is with TMS = 0.1?", "options": [ "3.0 s", "0.30 s", "0.15 s", "0.60 s" ], "answer": 1, "explanation": "t = 0.1 × 0.14 / (10^0.02 − 1) = 0.1 × 2.97 = 0.30 s.", "ref": "IEC 60255-151" }, { "id": "MV507-021", "module": "MV-507", "level": "P", "region": "All", "question": "Using the IEC very inverse curve, what is the trip time at 10 times Is with TMS = 0.2?", "options": [ "0.15 s", "1.5 s", "0.30 s", "0.45 s" ], "answer": 2, "explanation": "t = 0.2 × 13.5 / (10 − 1) = 0.30 s.", "ref": "IEC 60255-151" }, { "id": "MV507-022", "module": "MV-507", "level": "P", "region": "All", "question": "Using the IEC extremely inverse curve, what is the trip time at 5 times Is with TMS = 0.5?", "options": [ "3.33 s", "0.83 s", "4.0 s", "1.67 s" ], "answer": 3, "explanation": "t = 0.5 × 80 / (25 − 1) = 1.67 s.", "ref": "IEC 60255-151" }, { "id": "MV507-023", "module": "MV-507", "level": "P", "region": "All", "question": "A relay has a 400/1 CT and Is = 1.0 A. What is the plug setting multiplier for a 4,000 A fault?", "options": [ "4", "40", "10", "8" ], "answer": 2, "explanation": "Primary pickup is 400 A, so PSM = 4,000 / 400 = 10.", "ref": "" }, { "id": "MV507-024", "module": "MV-507", "level": "P", "region": "All", "question": "A relay has a 200/1 CT and Is = 0.75 A. What is the plug setting multiplier for an 1,800 A fault?", "options": [ "15", "9", "24", "12" ], "answer": 3, "explanation": "Primary pickup is 150 A, so PSM = 1,800 / 150 = 12.", "ref": "" }, { "id": "MV507-025", "module": "MV-507", "level": "P", "region": "All", "question": "What is the full load current of a 1500 kVA transformer on the 11 kV side?", "options": [ "78.7 A", "2,165 A", "136 A", "52.5 A" ], "answer": 0, "explanation": "I = 1,500 / (√3 × 11) = 78.7 A.", "ref": "" }, { "id": "MV507-026", "module": "MV-507", "level": "P", "region": "All", "question": "Taking inrush as 12 times rated current, what inrush point is plotted for a 1500 kVA, 11 kV transformer?", "options": [ "About 945 A at 0.1 s", "About 2,165 A at 0.1 s", "About 1,500 A at 1 s", "About 630 A at 0.1 s" ], "answer": 0, "explanation": "12 × 78.7 A = 945 A for about 0.1 s.", "ref": "" }, { "id": "MV507-027", "module": "MV-507", "level": "P", "region": "All", "question": "A 36 kA fault on a 400 V board is plotted on an 11 kV TCC. What current is shown?", "options": [ "13.1 kA", "36 kA", "990 A", "1,309 A" ], "answer": 3, "explanation": "36,000 × 0.4 / 11 = 1,309 A on the 11 kV base.", "ref": "" }, { "id": "MV507-028", "module": "MV-507", "level": "P", "region": "All", "question": "A downstream relay trips at 0.4 s for a fault and the grading margin is 0.3 s. What is the minimum upstream trip time at that fault current?", "options": [ "0.1 s", "1.2 s", "0.7 s", "0.4 s" ], "answer": 2, "explanation": "0.4 + 0.3 = 0.7 s.", "ref": "" }, { "id": "MV507-029", "module": "MV-507", "level": "P", "region": "All", "question": "Why is extremely inverse often chosen for a relay that must grade with downstream fuses?", "options": [ "Its shape is similar to a fuse curve, so they grade over a wide range", "It needs no CT", "It is the slowest at all currents", "It ignores inrush" ], "answer": 0, "explanation": "Fuse curves are steep, roughly I²t, like the EI curve.", "ref": "" }, { "id": "MV507-030", "module": "MV-507", "level": "P", "region": "All", "question": "What harmonic do transformer differential relays commonly use to block tripping during inrush?", "options": [ "2nd", "11th", "7th", "3rd" ], "answer": 0, "explanation": "Inrush current is rich in 2nd harmonic, while internal faults are not.", "ref": "" }, { "id": "MV507-031", "module": "MV-507", "level": "P", "region": "All", "question": "A 1 VA relay burden at 1 A rated secondary current equals what impedance?", "options": [ "5 Ω", "0.04 Ω", "1 Ω", "25 Ω" ], "answer": 2, "explanation": "Z = VA / I² = 1 / 1² = 1 Ω. At 5 A it would be only 0.04 Ω.", "ref": "" }, { "id": "MV507-032", "module": "MV-507", "level": "P", "region": "All", "question": "Why is a directional (67) element needed on parallel transformer feeders or closed rings?", "options": [ "To measure energy", "To block inrush", "So a healthy feeder does not trip for fault current flowing back through it", "To trip faster on overload" ], "answer": 2, "explanation": "Fault current can feed backwards through the healthy parallel path.", "ref": "" }, { "id": "MV507-033", "module": "MV-507", "level": "P", "region": "All", "question": "A transformer feeder high-set (50) element should be set...", "options": [ "Above inrush and above the maximum LV fault current referred to the HV side", "Below inrush", "At rated current", "At zero" ], "answer": 0, "explanation": "It then trips only for HV side faults, not for LV faults or energising.", "ref": "" }, { "id": "MV507-034", "module": "MV-507", "level": "P", "region": "All", "question": "Which ACB function gives a short delay so downstream breakers can clear first?", "options": [ "L", "I", "S", "G" ], "answer": 2, "explanation": "Short time (S) with its delay tsd provides selectivity for high currents.", "ref": "IEC 60947-2" }, { "id": "MV507-035", "module": "MV-507", "level": "P", "region": "All", "question": "Why do utilities often move from fuse switches to CB units above about 1000 to 1250 kVA?", "options": [ "Fuses are not made that large", "A CB and relay can grade with the LV ACB and add earth fault and transformer trips", "CBs are cheaper", "Fuses cause harmonics" ], "answer": 1, "explanation": "Large transformers need selective, adjustable protection.", "ref": "" }, { "id": "MV507-036", "module": "MV-507", "level": "E", "region": "All", "question": "Using the IEC standard inverse curve, what is the minimum TMS for 0.7 s at 10 times Is?", "options": [ "0.70", "0.35", "0.10", "0.24" ], "answer": 3, "explanation": "At 10 times Is, t = 2.97 × TMS, so TMS = 0.7 / 2.97 = 0.24.", "ref": "IEC 60255-151" }, { "id": "MV507-037", "module": "MV-507", "level": "E", "region": "All", "question": "A CT is 400/1 with a 20 kA maximum fault. Rct = 2 Ω, one-way lead resistance 0.15 Ω, relay 0.2 Ω and K = 2. What knee-point voltage is needed using Vk ≥ K·If·(Rct + 2RL + Rr)?", "options": [ "125 V", "500 V", "200 V", "250 V" ], "answer": 3, "explanation": "Secondary fault current = 50 A. Total = 2 + 0.3 + 0.2 = 2.5 Ω. Vk = 2 × 50 × 2.5 = 250 V.", "ref": "" }, { "id": "MV507-038", "module": "MV-507", "level": "E", "region": "All", "question": "For an LV phase-to-phase fault on a Dyn11 transformer, what does one HV phase carry relative to the equivalent three-phase fault current?", "options": [ "1.0 times", "0.5 times", "1.15 times", "0.87 times" ], "answer": 2, "explanation": "One HV phase carries 2/√3 = 1.15 times, so HV relays must grade for it.", "ref": "" }, { "id": "MV507-039", "module": "MV-507", "level": "E", "region": "All", "question": "Why can HV earth fault relays not see an LV earth fault on a Dyn transformer?", "options": [ "The CTs are too small", "Relays block it", "LV faults are too small", "The delta winding traps zero-sequence current, so no residual current flows on the HV side" ], "answer": 3, "explanation": "Use LV side earth fault or REF for LV winding earth faults.", "ref": "" }, { "id": "MV507-040", "module": "MV-507", "level": "E", "region": "All", "question": "For a delta-star transformer, what shift factor is applied to the ANSI damage curve when checking LV single-line-to-ground faults on the HV side?", "options": [ "0.58", "1.15", "1.0", "0.87" ], "answer": 0, "explanation": "For an LV ground fault the HV line current is 1/√3 = 0.58 per unit of the LV value, so the curve is shifted.", "ref": "IEEE C57.109" }, { "id": "MV507-041", "module": "MV-507", "level": "E", "region": "All", "question": "Under IEEE C57.109, roughly how long can a transformer withstand 25 times rated current on its thermal limit curve?", "options": [ "0.1 s", "2 s", "60 s", "10 s" ], "answer": 1, "explanation": "The thermal curve follows I²t = 1250 in per unit, which gives 2 s at 25 times.", "ref": "IEEE C57.109" }, { "id": "MV507-042", "module": "MV-507", "level": "E", "region": "All", "question": "How does a high-impedance REF scheme stay stable for an external fault when one CT saturates?", "options": [ "It is never stable", "It uses a 2nd harmonic filter", "It uses a longer TMS", "A stabilising resistor makes the relay voltage setting higher than the voltage the saturated CT can cause" ], "answer": 3, "explanation": "The setting voltage exceeds If × (Rct + 2RL), so the spill current flows through the saturated CT instead.", "ref": "" }, { "id": "MV507-043", "module": "MV-507", "level": "E", "region": "All", "question": "What does 5th harmonic restraint in a transformer differential relay guard against?", "options": [ "Inrush", "Earth faults", "Low frequency", "Overexcitation (overfluxing)" ], "answer": 3, "explanation": "Overexcitation produces strong 5th harmonic in the magnetising current.", "ref": "" }, { "id": "MV507-044", "module": "MV-507", "level": "E", "region": "All", "question": "Why must a transformer differential relay compensate for vector group?", "options": [ "To stop CT saturation", "For metering", "To raise sensitivity to inrush", "Because the HV and LV currents are phase-shifted by the winding connection" ], "answer": 3, "explanation": "Numerical relays apply software matrices, older schemes used delta-connected CTs.", "ref": "" }, { "id": "MV507-045", "module": "MV-507", "level": "E", "region": "All", "question": "What is the main benefit of zone selective interlocking between ACBs?", "options": [ "It lowers fault level", "It removes the need for CTs", "Lower cost", "The breaker nearest the fault trips without its short-time delay, while upstream breakers are restrained and keep their delay" ], "answer": 3, "explanation": "ZSI reduces fault energy at the busbars while keeping selectivity.", "ref": "" }, { "id": "MV507-046", "module": "MV-507", "level": "P", "region": "GCC", "question": "In the GCC, who usually sets the envelope that a consumer substation's protection must grade with?", "options": [ "The tenant", "The contractor", "The utility, based on its primary feeder relay settings", "The consultant only" ], "answer": 2, "explanation": "Utilities publish settings limits and often fix transformer feeder protection in their RMUs.", "ref": "" }, { "id": "MV507-047", "module": "MV-507", "level": "B", "region": "GCC", "question": "In a utility RMU supplying a GCC building transformer, who normally fixes the transformer feeder protection?", "options": [ "The architect", "Civil defence", "The utility standard", "The building's LV contractor" ], "answer": 2, "explanation": "The utility owns and sets the RMU, so the LV ACB settings must grade with it.", "ref": "" }, { "id": "MV507-048", "module": "MV-507", "level": "P", "region": "AU", "question": "In Australia, who typically requires a protection study for an HV customer installation?", "options": [ "The equipment supplier", "The local council", "The network operator", "The building certifier only" ], "answer": 2, "explanation": "Network operators specify protection and need a coordination study to connect.", "ref": "" }, { "id": "MV507-049", "module": "MV-507", "level": "B", "region": "NZ", "question": "Which document governs LV selectivity requirements in New Zealand installations?", "options": [ "IEC 60909", "AS/NZS 3000", "NZS 4219", "IEEE 80" ], "answer": 1, "explanation": "AS/NZS 3000 is cited by NZ regulations for LV installations.", "ref": "AS/NZS 3000" }, { "id": "MV507-050", "module": "MV-507", "level": "P", "region": "Asia", "question": "What do utilities such as TNB and SP Group expect with a consumer substation submission?", "options": [ "No protection data", "A protection coordination study with settings that grade with the utility", "Only a single line diagram", "A colour scheme" ], "answer": 1, "explanation": "They publish settings requirements and check grading with their feeders.", "ref": "" }, { "id": "MV507-051", "module": "MV-507", "level": "P", "region": "NZ", "question": "In New Zealand, who sets the protection requirements an HV customer installation must grade with?", "options": [ "The building owner only", "The local lines company", "The council", "EECA" ], "answer": 1, "explanation": "Lines companies specify protection and settings limits for HV connections.", "ref": "" }, { "id": "MV507-052", "module": "MV-507", "level": "E", "region": "AU", "question": "An Australian network feeder relay must clear a fault in 1.0 s and the customer relay trips at 0.6 s. What is the available grading margin?", "options": [ "1.6 s", "0.2 s", "0.4 s", "0.6 s" ], "answer": 2, "explanation": "1.0 − 0.6 = 0.4 s, which sits in the usual 0.3 to 0.4 s range.", "ref": "" }, { "id": "MV508-001", "module": "MV-508", "level": "B", "region": "All", "question": "What is ground potential rise (GPR)?", "options": [ "The voltage between phases", "The LV supply voltage", "The voltage of the neutral at no load", "The rise in voltage of the earth grid relative to remote earth during an earth fault" ], "answer": 3, "explanation": "GPR = IG × Rg.", "ref": "IEEE 80" }, { "id": "MV508-002", "module": "MV-508", "level": "B", "region": "All", "question": "What is touch voltage?", "options": [ "Between neutral and earth at no load", "Between a hand on earthed metal and the feet, normally 1 m away", "Between two feet 1 m apart", "Between phases" ], "answer": 1, "explanation": "Touch current passes across the chest, so limits are low.", "ref": "IEEE 80" }, { "id": "MV508-003", "module": "MV-508", "level": "B", "region": "All", "question": "What is step voltage?", "options": [ "Between two feet about 1 m apart on the ground", "Between two grids", "Between hand and feet", "Between the grid and remote earth" ], "answer": 0, "explanation": "It comes from the slope of the ground surface potential.", "ref": "IEEE 80" }, { "id": "MV508-004", "module": "MV-508", "level": "B", "region": "All", "question": "Which tolerable voltage limit is usually lower?", "options": [ "Neither has a limit", "Touch", "They are equal", "Step" ], "answer": 1, "explanation": "Touch current flows through the heart region, so touch limits are much lower.", "ref": "IEEE 80" }, { "id": "MV508-005", "module": "MV-508", "level": "B", "region": "All", "question": "Why is crushed rock laid in outdoor substations?", "options": [ "To lower grid resistance", "To add foot contact resistance and raise tolerable step and touch voltages", "To cool equipment", "For drainage only" ], "answer": 1, "explanation": "A high-resistivity surface layer is in series with the feet.", "ref": "IEEE 80" }, { "id": "MV508-006", "module": "MV-508", "level": "B", "region": "All", "question": "What happens to tolerable touch and step voltages if fault clearing is faster?", "options": [ "They fall", "No change", "They rise", "They become zero" ], "answer": 2, "explanation": "Limits scale with 1/√t, so faster clearing allows higher voltages.", "ref": "IEEE 80" }, { "id": "MV508-007", "module": "MV-508", "level": "B", "region": "All", "question": "Halving the fault clearing time raises tolerable voltages by about...", "options": [ "4 times", "1.41 times", "2 times", "1.2 times" ], "answer": 1, "explanation": "1/√0.5 = 1.41.", "ref": "IEEE 80" }, { "id": "MV508-008", "module": "MV-508", "level": "B", "region": "All", "question": "What body resistance does IEEE 80 use for step and touch calculations?", "options": [ "10,000 Ω", "1,000 Ω", "100 Ω", "500 Ω" ], "answer": 1, "explanation": "IEEE 80 takes 1,000 Ω for hand to feet and foot to foot.", "ref": "IEEE 80" }, { "id": "MV508-009", "module": "MV-508", "level": "B", "region": "All", "question": "Which body weight gives the more conservative IEEE 80 limits?", "options": [ "100 kg", "70 kg", "Weight has no effect", "50 kg" ], "answer": 3, "explanation": "The 50 kg constant 0.116 is lower than the 70 kg constant 0.157.", "ref": "IEEE 80" }, { "id": "MV508-010", "module": "MV-508", "level": "B", "region": "All", "question": "What does closer earth grid conductor spacing do?", "options": [ "Raises mesh voltage", "Lowers mesh voltage by flattening the surface potential", "Raises GPR", "Has no effect" ], "answer": 1, "explanation": "Smaller meshes reduce the potential dip between conductors.", "ref": "IEEE 80" }, { "id": "MV508-011", "module": "MV-508", "level": "B", "region": "All", "question": "Where is the mesh (touch) voltage usually highest in a grid?", "options": [ "At the grid centre", "In the middle of a corner mesh", "At remote earth", "Over a conductor" ], "answer": 1, "explanation": "Corner meshes have the largest potential dip.", "ref": "IEEE 80" }, { "id": "MV508-012", "module": "MV-508", "level": "B", "region": "All", "question": "What does the current split factor Sf represent?", "options": [ "Rod length ratio", "The fraction of earth fault current that flows into the grid rather than returning by other paths", "Body weight", "The soil layer ratio" ], "answer": 1, "explanation": "Cable screens and overhead earth wires carry part of the current back to the source.", "ref": "IEEE 80" }, { "id": "MV508-013", "module": "MV-508", "level": "B", "region": "All", "question": "Which test method is widely used to measure soil resistivity?", "options": [ "Clamp meter", "The Wenner four-pin method", "Megger insulation test", "Thermal imaging" ], "answer": 1, "explanation": "Four equally spaced pins are used at several spacings.", "ref": "IEEE 81" }, { "id": "MV508-014", "module": "MV-508", "level": "B", "region": "All", "question": "Why are earth rods useful in high-resistivity surface soil?", "options": [ "They replace the grid", "They reduce fault current", "They reach deeper, lower-resistivity layers", "They look good" ], "answer": 2, "explanation": "Rods also help stabilise grid resistance against seasonal drying.", "ref": "" }, { "id": "MV508-015", "module": "MV-508", "level": "B", "region": "All", "question": "Which jointing method is commonly used for permanent buried earth grid connections?", "options": [ "Insulating tape", "Soldering only", "Twisting", "Exothermic welding or approved compression connectors" ], "answer": 3, "explanation": "Buried joints must survive corrosion and fault current heating.", "ref": "IEEE 80" }, { "id": "MV508-016", "module": "MV-508", "level": "B", "region": "All", "question": "Why must the substation fence be considered in earthing design?", "options": [ "It is decorative", "It sets the fault level", "People outside can touch it, so touch voltage at the fence must be safe", "It carries load current" ], "answer": 2, "explanation": "Fences are either bonded with a grading conductor outside or isolated from the grid.", "ref": "IEEE 80" }, { "id": "MV508-017", "module": "MV-508", "level": "B", "region": "All", "question": "What is a transferred potential?", "options": [ "A voltage carried outside the substation by metal paths such as cables, pipes or rails", "A capacitor voltage", "The relay voltage", "The LV phase voltage" ], "answer": 0, "explanation": "Remote people can be exposed to part of the GPR through conductive services.", "ref": "IEEE 80" }, { "id": "MV508-018", "module": "MV-508", "level": "B", "region": "All", "question": "Which soil generally has the highest resistivity?", "options": [ "Wet clay", "Wet loam", "Dry sand or rock", "Seawater-saturated soil" ], "answer": 2, "explanation": "Low moisture and few dissolved salts mean high resistivity.", "ref": "" }, { "id": "MV508-019", "module": "MV-508", "level": "B", "region": "All", "question": "Which method is commonly used to measure the resistance of an earth electrode?", "options": [ "Insulation resistance test", "Partial discharge", "Tan delta", "The fall-of-potential method" ], "answer": 3, "explanation": "Current and potential probes are placed away from the electrode.", "ref": "IEEE 81" }, { "id": "MV508-020", "module": "MV-508", "level": "P", "region": "All", "question": "IEEE 80 tolerable touch voltage for 50 kg with no surface layer, soil ρ = 100 Ω·m and ts = 0.5 s is about...", "options": [ "189 V", "681 V", "262 V", "116 V" ], "answer": 0, "explanation": "(1000 + 1.5 × 100) × 0.116 / √0.5 = 1150 × 0.164 = 189 V.", "ref": "IEEE 80" }, { "id": "MV508-021", "module": "MV-508", "level": "P", "region": "All", "question": "IEEE 80 tolerable step voltage for 50 kg with no surface layer, soil ρ = 100 Ω·m and ts = 0.5 s is about...", "options": [ "262 V", "681 V", "350 V", "189 V" ], "answer": 0, "explanation": "(1000 + 6 × 100) × 0.116 / √0.5 = 1600 × 0.164 = 262 V.", "ref": "IEEE 80" }, { "id": "MV508-022", "module": "MV-508", "level": "P", "region": "All", "question": "What is the Dalziel tolerable body current for a 50 kg person with a 0.5 s fault?", "options": [ "0.116 A", "0.164 A", "0.058 A", "0.232 A" ], "answer": 1, "explanation": "IB = 0.116 / √0.5 = 0.164 A.", "ref": "IEEE 80" }, { "id": "MV508-023", "module": "MV-508", "level": "P", "region": "All", "question": "A fault of 10,000 A (3I0) has a split factor of 0.6 and the grid resistance is 0.5 Ω. Ignoring decrement, what is the GPR?", "options": [ "3,000 V", "5,000 V", "10,000 V", "6,000 V" ], "answer": 0, "explanation": "IG = 0.6 × 10,000 = 6,000 A and GPR = 6,000 × 0.5 = 3,000 V.", "ref": "IEEE 80" }, { "id": "MV508-024", "module": "MV-508", "level": "P", "region": "All", "question": "If the GPR is below the tolerable touch voltage, what does IEEE 80 suggest?", "options": [ "Remove the grid", "The design is unsafe", "Double the fault current", "No further mesh and step analysis is needed, apart from transferred potentials" ], "answer": 3, "explanation": "If even the full GPR is tolerable, mesh and step voltages will be too.", "ref": "IEEE 80" }, { "id": "MV508-025", "module": "MV-508", "level": "P", "region": "All", "question": "What is the soil resistivity from a Wenner test with 3 m pin spacing and a reading of 5 Ω?", "options": [ "188 Ω·m", "94 Ω·m", "15 Ω·m", "47 Ω·m" ], "answer": 1, "explanation": "ρ = 2πaR = 2π × 3 × 5 = 94.2 Ω·m.", "ref": "IEEE 81" }, { "id": "MV508-026", "module": "MV-508", "level": "P", "region": "All", "question": "In a Wenner test, what does a larger pin spacing mainly show?", "options": [ "Rod corrosion", "Surface moisture only", "Resistivity of deeper soil", "Grid resistance" ], "answer": 2, "explanation": "Current spreads deeper as the spacing grows, roughly to a depth similar to the spacing.", "ref": "IEEE 81" }, { "id": "MV508-027", "module": "MV-508", "level": "P", "region": "All", "question": "In the fall-of-potential test, at what distance is the potential probe often placed for a small electrode in uniform soil?", "options": [ "100%", "10% of the current probe distance", "About 62% of the current probe distance", "150%" ], "answer": 2, "explanation": "The 61.8% rule gives the true resistance in uniform soil.", "ref": "IEEE 81" }, { "id": "MV508-028", "module": "MV-508", "level": "P", "region": "All", "question": "What surface layer derating factor Cs results from ρ = 100 Ω·m, ρs = 3,000 Ω·m and hs = 0.1 m using Cs = 1 − 0.09(1 − ρ/ρs)/(2hs + 0.09)?", "options": [ "0.90", "0.60", "0.50", "0.70" ], "answer": 3, "explanation": "0.09 × 0.967 / 0.29 = 0.30, so Cs = 0.70.", "ref": "IEEE 80" }, { "id": "MV508-029", "module": "MV-508", "level": "P", "region": "All", "question": "Why is the decrement factor Df used in IEEE 80?", "options": [ "To size the fence", "To include the DC offset in the early fault current", "To reduce soil resistivity", "To allow for body weight" ], "answer": 1, "explanation": "IG = Df × Sf × 3I0, and Df rises as fault duration shortens or X/R rises.", "ref": "IEEE 80" }, { "id": "MV508-030", "module": "MV-508", "level": "P", "region": "All", "question": "Why is soil resistivity ideally measured or adjusted for the dry season?", "options": [ "It is easier to drive pins", "Dry soil has higher resistivity, giving the worst case", "Standards forbid wet testing", "Wet soil cannot be tested" ], "answer": 1, "explanation": "Seasonal drying raises grid resistance and GPR.", "ref": "" }, { "id": "MV508-031", "module": "MV-508", "level": "P", "region": "All", "question": "Why should earth grid conductors be buried at about 0.5 to 0.8 m?", "options": [ "To raise GPR", "To reduce cost only", "To raise step voltage", "To protect them mechanically and keep them in more stable, moister soil" ], "answer": 3, "explanation": "Deeper burial also lowers step voltage slightly.", "ref": "IEEE 80" }, { "id": "MV508-032", "module": "MV-508", "level": "P", "region": "All", "question": "What is the purpose of a grading ring outside a bonded substation fence?", "options": [ "To control the touch voltage for someone standing outside the fence", "To support the fence", "To reduce lightning", "To carry load current" ], "answer": 0, "explanation": "A buried conductor about 1 m outside the fence raises the ground potential there.", "ref": "IEEE 80" }, { "id": "MV508-033", "module": "MV-508", "level": "P", "region": "All", "question": "Why can a clamp-on earth tester give misleading results on a single isolated electrode?", "options": [ "It needs a parallel return path to complete the loop", "It needs DC", "It works only at LV", "It measures resistivity only" ], "answer": 0, "explanation": "Clamp-on testers measure loop resistance and need other earthed paths in parallel.", "ref": "" }, { "id": "MV508-034", "module": "MV-508", "level": "E", "region": "All", "question": "IEEE 80 tolerable touch voltage for 50 kg with Cs = 0.70, ρs = 3,000 Ω·m and ts = 0.5 s is about...", "options": [ "921 V", "681 V", "189 V", "450 V" ], "answer": 1, "explanation": "(1000 + 1.5 × 0.70 × 3,000) × 0.116 / √0.5 = 4,150 × 0.164 = 681 V.", "ref": "IEEE 80" }, { "id": "MV508-035", "module": "MV-508", "level": "E", "region": "All", "question": "For the same surface layer (Cs = 0.70, ρs = 3,000 Ω·m, ts = 0.5 s), what is the 70 kg tolerable touch voltage?", "options": [ "921 V", "760 V", "1,250 V", "681 V" ], "answer": 0, "explanation": "4,150 × 0.157 / √0.5 = 921 V.", "ref": "IEEE 80" }, { "id": "MV508-036", "module": "MV-508", "level": "E", "region": "All", "question": "Using IEEE 80 with Kf = 7.00 for annealed soft-drawn copper, what conductor size carries 10 kA for 0.5 s?", "options": [ "About 50 mm² (99 kcmil)", "About 25 mm² (49.5 kcmil)", "About 70 mm²", "About 12 mm²" ], "answer": 1, "explanation": "A = I × Kf × √tc = 10 × 7.00 × 0.707 = 49.5 kcmil, which is about 25 mm².", "ref": "IEEE 80" }, { "id": "MV508-037", "module": "MV-508", "level": "E", "region": "All", "question": "What is the resistance of a single 3 m rod, 16 mm in diameter, in 100 Ω·m soil using R = ρ/(2πL) × (ln(8L/d) − 1)?", "options": [ "11 Ω", "33 Ω", "53 Ω", "22 Ω" ], "answer": 1, "explanation": "ρ/(2πL) = 5.31 and ln(1500) − 1 = 6.31, so R = 33.5 Ω.", "ref": "IEEE 80" }, { "id": "MV508-038", "module": "MV-508", "level": "E", "region": "All", "question": "For a 300 m² grid in 100 Ω·m soil with 170 m of buried conductor at 0.6 m, what grid resistance does the Sverak formula give?", "options": [ "3.0 Ω", "0.3 Ω", "10 Ω", "1.0 Ω" ], "answer": 0, "explanation": "Rg = ρ[1/LT + 1/√(20A) × (1 + 1/(1 + h√(20/A)))] = 3.0 Ω.", "ref": "IEEE 80" }, { "id": "MV508-039", "module": "MV-508", "level": "E", "region": "All", "question": "Which factor dominates grid resistance for a given soil resistivity?", "options": [ "Burial depth", "Conductor diameter", "Grid area", "Conductor material" ], "answer": 2, "explanation": "Rg falls roughly with 1/√A, so area matters far more than adding conductor inside it.", "ref": "IEEE 80" }, { "id": "MV508-040", "module": "MV-508", "level": "E", "region": "All", "question": "What does the IEEE 80 mesh voltage formula Em = ρ·Km·Ki·IG/LM show about adding conductor length?", "options": [ "It has no effect", "It changes only the step voltage", "It raises the mesh voltage", "More effective buried length LM lowers the mesh voltage" ], "answer": 3, "explanation": "Longer effective length spreads the current and flattens the potential.", "ref": "IEEE 80" }, { "id": "MV508-041", "module": "MV-508", "level": "E", "region": "All", "question": "In two-layer soil with a high-resistivity top layer over a low-resistivity bottom layer, what usually helps most?", "options": [ "A larger shallow grid only", "Long rods reaching the lower layer", "A thinner surface layer", "Removing rods" ], "answer": 1, "explanation": "Rods into the low-resistivity layer cut grid resistance strongly.", "ref": "" }, { "id": "MV508-042", "module": "MV-508", "level": "E", "region": "All", "question": "How does a large number of cable screens leaving a substation affect the split factor?", "options": [ "It raises Sf toward 1", "It lowers Sf because more current returns through the screens", "No effect", "It makes Sf negative" ], "answer": 1, "explanation": "More metallic return paths reduce the current into the local grid.", "ref": "IEEE 80" }, { "id": "MV508-043", "module": "MV-508", "level": "B", "region": "GCC", "question": "Why are deep rods or enhanced earthing compounds often used in GCC desert sites?", "options": [ "To save copper", "Dry surface sand has very high resistivity", "To reduce fault current", "Rules ban grids" ], "answer": 1, "explanation": "Deeper moist layers have much lower resistivity.", "ref": "" }, { "id": "MV508-044", "module": "MV-508", "level": "P", "region": "GCC", "question": "Which earthing references are common in GCC substation design?", "options": [ "Only AS 2067", "Only NZS 4219", "IEC 60909 only", "IEEE 80 and BS EN 50522, plus utility rules" ], "answer": 3, "explanation": "Utilities add rules on earth pit construction, testing and maximum resistance.", "ref": "" }, { "id": "MV508-045", "module": "MV-508", "level": "B", "region": "GCC", "question": "Who usually sets the maximum earth resistance and earth pit details for a GCC distribution substation?", "options": [ "The cable supplier", "The tenant", "The architect", "The utility's standards" ], "answer": 3, "explanation": "Each utility has its own earthing requirements for distribution substations.", "ref": "" }, { "id": "MV508-046", "module": "MV-508", "level": "B", "region": "AU", "question": "Which approach is mainly used in Australia for substation earthing safety?", "options": [ "IEC 60909", "No standard", "The risk-based ENA EG-0 method with AS 2067", "IEEE 80 only" ], "answer": 2, "explanation": "EG-0 sets touch voltage limits based on the probability of contact and fault frequency.", "ref": "ENA EG-0" }, { "id": "MV508-047", "module": "MV-508", "level": "P", "region": "AU", "question": "How does ENA EG-0 set touch voltage limits compared with IEEE 80?", "options": [ "From the risk of fatality, using fault frequency and contact probability", "From body weight only", "From soil resistivity only", "One fixed value for all sites" ], "answer": 0, "explanation": "Limits are relaxed where contact is unlikely and tightened where people gather.", "ref": "ENA EG-0" }, { "id": "MV508-048", "module": "MV-508", "level": "P", "region": "NZ", "question": "Which risk-based earthing approach is used in New Zealand alongside AS 2067?", "options": [ "ENA EG-0 based guidance", "IS 3043", "NZS 4219", "IEC 60909" ], "answer": 0, "explanation": "NZ practice follows the risk-based EG-0 approach with AS 2067.", "ref": "AS 2067" }, { "id": "MV508-049", "module": "MV-508", "level": "B", "region": "Asia", "question": "Which Indian standard covers earthing practice?", "options": [ "IS 3043", "IS 732", "IS 2026", "IS 1255" ], "answer": 0, "explanation": "IS 3043 is the Indian code of practice for earthing.", "ref": "IS 3043" }, { "id": "MV508-050", "module": "MV-508", "level": "P", "region": "All", "question": "Which British standard gives the code of practice for protective earthing of electrical installations?", "options": [ "BS 7671 only", "BS 5839", "BS 7430", "BS 6651" ], "answer": 2, "explanation": "BS 7430 covers earth electrodes and earthing design and testing.", "ref": "BS 7430" }, { "id": "MV508-051", "module": "MV-508", "level": "P", "region": "All", "question": "Why are HV and LV earths sometimes kept separate at a distribution substation?", "options": [ "To avoid testing", "Because a high EPR on a combined earth could appear on LV neutrals in the building", "To save copper", "To raise fault current" ], "answer": 1, "explanation": "Codes allow a combined earth only when the EPR stays within set limits.", "ref": "EN 50522" }, { "id": "MV509-001", "module": "MV-509", "level": "B", "region": "All", "question": "What does an insulation resistance test measure?", "options": [ "The resistance of the conductor", "The contact resistance of a breaker", "The earth grid resistance", "The resistance of the insulation between conductor and earth or between conductors" ], "answer": 3, "explanation": "A DC voltage is applied across the insulation and the leakage current gives the resistance, usually in megohms or gigohms.", "ref": "IEEE 43" }, { "id": "MV509-002", "module": "MV-509", "level": "B", "region": "All", "question": "How is the polarisation index (PI) calculated?", "options": [ "IR multiplied by temperature", "IR at 10 minutes divided by IR at 1 minute", "IR at 60 seconds divided by IR at 30 seconds", "IR at 1 minute divided by IR at 10 minutes" ], "answer": 1, "explanation": "PI = R10 min / R1 min. A rising reading over time shows clean, dry insulation.", "ref": "IEEE 43" }, { "id": "MV509-003", "module": "MV-509", "level": "B", "region": "All", "question": "An IR test gives 800 MΩ at 1 minute and 2,400 MΩ at 10 minutes. What is the PI?", "options": [ "3.0", "2.0", "1,600", "0.33" ], "answer": 0, "explanation": "PI = 2,400 / 800 = 3.0, which is generally a good result.", "ref": "IEEE 43" }, { "id": "MV509-004", "module": "MV-509", "level": "B", "region": "All", "question": "How is the dielectric absorption ratio (DAR) usually calculated?", "options": [ "IR at 1 minute divided by IR at 15 seconds only for cables", "IR at 60 seconds divided by IR at 30 seconds", "IR at 10 minutes divided by IR at 1 minute", "Leakage current divided by voltage" ], "answer": 1, "explanation": "DAR is a quicker version of the PI, using the 60 second and 30 second readings.", "ref": "" }, { "id": "MV509-005", "module": "MV-509", "level": "B", "region": "All", "question": "A PI below 1.0 usually means...", "options": [ "Very good insulation", "The test voltage was too high", "Insulation that is likely wet, contaminated or damaged", "The instrument is overranging" ], "answer": 2, "explanation": "IR that falls with time points to moisture or contamination and needs investigation before energising.", "ref": "" }, { "id": "MV509-006", "module": "MV-509", "level": "B", "region": "All", "question": "Why is VLF testing done at 0.1 Hz instead of 50 Hz?", "options": [ "It finds more faults", "It needs about 500 times less charging power for long cables", "It is required for LV cables", "It avoids the need for earthing" ], "answer": 1, "explanation": "Capacitive charging power is proportional to frequency, so 0.1 Hz needs about 1/500 of the 50 Hz power.", "ref": "IEEE 400.2" }, { "id": "MV509-007", "module": "MV-509", "level": "B", "region": "All", "question": "What is a common VLF withstand voltage for a new 6.35/11 kV XLPE cable?", "options": [ "About 33 kV rms", "About 50 kV DC", "About 19 kV rms (3 U0)", "About 6 kV rms" ], "answer": 2, "explanation": "3 x 6.35 kV = 19 kV rms, usually for 15 to 60 minutes. Use the utility or project value.", "ref": "IEEE 400.2" }, { "id": "MV509-008", "module": "MV-509", "level": "B", "region": "All", "question": "What does a transformer turns ratio (TTR) test check?", "options": [ "The earth resistance", "Oil quality", "Winding temperature", "The voltage ratio of each phase on each tap against the nameplate" ], "answer": 3, "explanation": "The measured ratio should match the calculated nameplate ratio closely on every tap position.", "ref": "IEC 60076-1" }, { "id": "MV509-009", "module": "MV-509", "level": "B", "region": "All", "question": "What is the usual acceptance tolerance for a transformer turns ratio test?", "options": [ "Within 5% of nameplate", "Any value is fine", "Within 0.5% of nameplate", "Within 10% of nameplate" ], "answer": 2, "explanation": "IEC 60076-1 and NETA both use about 0.5% of the declared ratio.", "ref": "IEC 60076-1" }, { "id": "MV509-010", "module": "MV-509", "level": "B", "region": "All", "question": "Winding resistance readings on the three phases of a transformer should normally agree within about...", "options": [ "50%", "2%", "25%", "10%" ], "answer": 1, "explanation": "A larger difference points to a loose joint, poor tap changer contact or a damaged winding.", "ref": "ANSI/NETA ATS" }, { "id": "MV509-011", "module": "MV-509", "level": "B", "region": "All", "question": "What does secondary injection of a protection relay prove?", "options": [ "CT ratio and polarity", "Cable insulation", "Busbar contact resistance", "Relay pickup, timing and trip outputs against the settings" ], "answer": 3, "explanation": "A test set injects current and voltage into the relay inputs and times the trip outputs.", "ref": "IEC 60255-151" }, { "id": "MV509-012", "module": "MV-509", "level": "B", "region": "All", "question": "What does an ITP stand for in commissioning?", "options": [ "Insulation Test Procedure", "Initial Transformer Protection", "Inspection and Test Plan", "Integrated Testing Process" ], "answer": 2, "explanation": "The ITP lists each inspection and test, the acceptance criteria, the records and the hold and witness points.", "ref": "" }, { "id": "MV509-013", "module": "MV-509", "level": "B", "region": "All", "question": "Why is contact resistance measured on MV switchgear?", "options": [ "To measure insulation", "To check relay timing", "To find poor main contacts or bolted joints that would overheat under load", "To check the earth grid" ], "answer": 2, "explanation": "A micro-ohmmeter passes a high DC current through the main circuit and reads the voltage drop.", "ref": "" }, { "id": "MV509-014", "module": "MV-509", "level": "B", "region": "All", "question": "What does a cable oversheath test check?", "options": [ "The conductor insulation", "Tan delta", "Phase rotation", "The integrity of the outer sheath so water cannot reach the screen" ], "answer": 3, "explanation": "A DC voltage is applied between the metallic screen and earth to find sheath damage after laying.", "ref": "IEC 60229" }, { "id": "MV509-015", "module": "MV-509", "level": "B", "region": "All", "question": "What is checked on SF6 switchgear before energising?", "options": [ "Battery acid level", "Gas pressure or density reading in the correct band", "Breather colour", "Oil level" ], "answer": 1, "explanation": "The density gauge must be in the green zone, and moisture and purity are checked when gas is handled on site.", "ref": "IEC 62271-4" }, { "id": "MV509-016", "module": "MV-509", "level": "B", "region": "All", "question": "Why must the temperature be recorded with every IR reading?", "options": [ "For the report cover", "To set the VLF voltage", "IR changes strongly with temperature, so results must be corrected before comparison", "It has no effect" ], "answer": 2, "explanation": "For many insulations IR roughly halves for every 10 K rise.", "ref": "IEEE 43" }, { "id": "MV509-017", "module": "MV-509", "level": "B", "region": "All", "question": "What does a phasing test on an MV cable confirm?", "options": [ "The cable is dry", "Each core connects to the correct phase at both ends", "The tan delta value", "The sheath is intact" ], "answer": 1, "explanation": "Wrong phasing would short two sources together when a ring or NOP is closed.", "ref": "" }, { "id": "MV509-018", "module": "MV-509", "level": "B", "region": "GCC", "question": "In most GCC utilities, who usually witnesses MV cable tests before energisation?", "options": [ "Nobody", "The insurer only", "The utility inspector, using the utility test formats", "The architect" ], "answer": 2, "explanation": "Utilities such as DEWA and ADDC witness tests and require their own test records before energising.", "ref": "" }, { "id": "MV509-019", "module": "MV-509", "level": "B", "region": "All", "question": "Which DC test voltage is typical for an IR test on 11 kV switchgear or cable?", "options": [ "250 V", "50 kV", "5 kV", "500 V" ], "answer": 2, "explanation": "IEEE 43 suggests 2.5 to 5 kV DC for equipment rated 5 to 12 kV, and 5 kV is a common choice.", "ref": "IEEE 43" }, { "id": "MV509-020", "module": "MV-509", "level": "P", "region": "All", "question": "A 400/1 CT feeds a relay set to pick up at 1.0 A secondary. What primary current does that represent?", "options": [ "400 A", "100 A", "1 A", "4,000 A" ], "answer": 0, "explanation": "1.0 A secondary x 400 = 400 A primary.", "ref": "" }, { "id": "MV509-021", "module": "MV-509", "level": "P", "region": "All", "question": "An IEC standard inverse relay has TMS 0.1. What is the trip time at 10 times setting?", "options": [ "About 0.1 s", "About 3.0 s", "About 0.3 s", "About 1.0 s" ], "answer": 2, "explanation": "t = 0.1 x 0.14 / (10^0.02 - 1) = 0.297 s.", "ref": "IEC 60255-151" }, { "id": "MV509-022", "module": "MV-509", "level": "P", "region": "All", "question": "An 11,000/433 V Dyn11 transformer is tested phase by phase. The HV winding is delta and the LV winding is star. What per-phase ratio should the TTR read?", "options": [ "44.00", "19.05", "14.67", "25.40" ], "answer": 0, "explanation": "Per phase it compares 11,000 V across the delta winding with 433/√3 = 250 V across the star winding: 44.0.", "ref": "IEC 60076-1" }, { "id": "MV509-023", "module": "MV-509", "level": "P", "region": "All", "question": "On an 11,000/433 V transformer the line-to-line ratio reads 25.52. What is the error against nameplate?", "options": [ "About 4.6%", "About 0.46%", "About 1.2%", "About 0.05%" ], "answer": 1, "explanation": "Nameplate ratio is 25.404. (25.52 - 25.404) / 25.404 = 0.46%, just inside 0.5%.", "ref": "IEC 60076-1" }, { "id": "MV509-024", "module": "MV-509", "level": "P", "region": "All", "question": "Winding resistances read 0.512, 0.518 and 0.540 Ω. What is the spread against the average?", "options": [ "About 1%", "About 5.4%", "About 2%", "About 12%" ], "answer": 1, "explanation": "(0.540 - 0.512) / 0.523 = 5.4%, well above the usual 2%, so investigate that phase.", "ref": "ANSI/NETA ATS" }, { "id": "MV509-025", "module": "MV-509", "level": "P", "region": "All", "question": "What does a vector group test confirm on a Dyn11 transformer?", "options": [ "That HV and LV are in phase", "That the neutral is earthed", "That LV leads HV by 30°", "That LV lags HV by 30°" ], "answer": 2, "explanation": "Clock position 11 means the LV phasor sits at 11 o'clock, 30° ahead of HV.", "ref": "IEC 60076-1" }, { "id": "MV509-026", "module": "MV-509", "level": "P", "region": "All", "question": "What does primary injection prove that secondary injection cannot?", "options": [ "Relay firmware version", "Battery voltage", "The full chain from CT primary through wiring to the relay, including CT ratio and polarity", "Relay curve shape" ], "answer": 2, "explanation": "Current is passed through the CT primary, so the whole measuring circuit is proved.", "ref": "" }, { "id": "MV509-027", "module": "MV-509", "level": "P", "region": "All", "question": "What is the knee point of a protection CT, as defined in IEC 61869-2?", "options": [ "The voltage where a 10% rise causes a 50% rise in exciting current", "The point where ratio error is zero", "The voltage at rated current", "The rated burden" ], "answer": 0, "explanation": "Above the knee point the CT core saturates quickly.", "ref": "IEC 61869-2" }, { "id": "MV509-028", "module": "MV-509", "level": "P", "region": "All", "question": "Which set of tests is usually done on a protection CT at site?", "options": [ "Ratio, polarity, magnetisation curve and insulation", "Tan delta and PD only", "Oil BDV and DGA", "Earth resistance only" ], "answer": 0, "explanation": "These prove the CT will measure correctly and saturate where expected.", "ref": "IEC 61869-2" }, { "id": "MV509-029", "module": "MV-509", "level": "P", "region": "All", "question": "Healthy XLPE cable shows what tan delta pattern as VLF voltage rises from 0.5 U0 to 1.5 U0?", "options": [ "Values that fall to zero", "Random readings", "Low, stable values with very little rise", "Values that rise sharply" ], "answer": 2, "explanation": "Low mean, low standard deviation and small tip-up all indicate good condition.", "ref": "IEEE 400.2" }, { "id": "MV509-030", "module": "MV-509", "level": "P", "region": "All", "question": "Under IEEE 400.2-2013, what tip-up limit (1.5 U0 minus 0.5 U0) puts PE-based cable in the no action class?", "options": [ "Below 5 x 10^-3", "Below 1%", "Below 50 x 10^-3", "Below 0.5" ], "answer": 0, "explanation": "No action needs tip-up under 5 x 10^-3, stability under 0.1 x 10^-3 and mean at U0 under 4 x 10^-3. Check the current edition.", "ref": "IEEE 400.2" }, { "id": "MV509-031", "module": "MV-509", "level": "P", "region": "All", "question": "Unstable tan delta readings (high standard deviation at one voltage) usually point to...", "options": [ "A perfect cable", "Water trees in the insulation", "Low ambient temperature", "Moisture or contamination in joints or terminations" ], "answer": 3, "explanation": "Unstable readings suggest a local problem in accessories, while steady tip-up points to water trees.", "ref": "IEEE 400.2" }, { "id": "MV509-032", "module": "MV-509", "level": "P", "region": "All", "question": "What DC test does IEC 60502-2 give for the oversheath after installation?", "options": [ "1 kV for 1 hour", "4 kV per mm of sheath thickness, maximum 10 kV, for 1 minute", "3 U0 at 0.1 Hz for 60 minutes", "50 kV for 15 minutes" ], "answer": 1, "explanation": "This proves the oversheath, applied between the screen and earth.", "ref": "IEC 60502-2" }, { "id": "MV509-033", "module": "MV-509", "level": "P", "region": "All", "question": "IEC 62271-200 allows a power frequency test on site after erection of MV switchgear. For 12 kV gear with a 28 kV factory test, what is the site value?", "options": [ "42 kV", "14 kV", "28 kV", "22.4 kV" ], "answer": 3, "explanation": "The site test is 80% of the factory value: 0.8 x 28 = 22.4 kV.", "ref": "IEC 62271-200" }, { "id": "MV509-034", "module": "MV-509", "level": "P", "region": "All", "question": "Why is a high DC withstand test no longer recommended for aged XLPE cables?", "options": [ "It can leave space charge that later helps failures in service", "DC is too slow", "DC cannot reach the voltage", "It needs too much power" ], "answer": 0, "explanation": "DC testing of service-aged XLPE has been linked to failures after return to service, so AC or VLF is preferred.", "ref": "IEEE 400.2" }, { "id": "MV509-035", "module": "MV-509", "level": "P", "region": "GCC", "question": "Why do high site temperatures in the GCC matter for insulation testing?", "options": [ "They increase the PI", "IR readings fall at high temperature, so readings must be temperature corrected before comparison", "They do not matter", "They change the VLF frequency" ], "answer": 1, "explanation": "A cable at 45°C may read far lower than at 20°C with no defect present.", "ref": "" }, { "id": "MV509-036", "module": "MV-509", "level": "P", "region": "AU", "question": "In Australia, who usually sets the test method and voltage for new cables connected to the network?", "options": [ "The builder", "The local council", "The cable manufacturer only", "The network operator (DNSP) in its specifications" ], "answer": 3, "explanation": "Each DNSP publishes its own commissioning requirements, with VLF and tan delta widely used.", "ref": "" }, { "id": "MV509-037", "module": "MV-509", "level": "P", "region": "Asia", "question": "In Singapore, which utility witnesses tests before connecting a new MV intake?", "options": [ "Meralco", "SP Group (SP PowerGrid)", "TNB", "CLP" ], "answer": 1, "explanation": "SP Group publishes its requirements and witnesses tests before energisation.", "ref": "" }, { "id": "MV509-038", "module": "MV-509", "level": "E", "region": "All", "question": "A copper winding reads 0.500 Ω at 75°C. What is it at 20°C?", "options": [ "0.608 Ω", "0.367 Ω", "0.500 Ω", "0.411 Ω" ], "answer": 3, "explanation": "R20 = 0.500 x (234.5 + 20) / (234.5 + 75) = 0.411 Ω.", "ref": "IEC 60076-1" }, { "id": "MV509-039", "module": "MV-509", "level": "E", "region": "All", "question": "Why can modern XLPE cable show a PI near 1.0 and still be in good condition?", "options": [ "PI is never used for cables", "XLPE is always wet", "XLPE has very little absorption current, so IR is very high from the start and barely rises", "The test set is wrong" ], "answer": 2, "explanation": "With very high IR values the absorption effect is small, so look at the absolute IR value as well.", "ref": "IEEE 43" }, { "id": "MV509-040", "module": "MV-509", "level": "E", "region": "All", "question": "Why is tan delta alone not enough to find a single bad joint on a long cable?", "options": [ "Tan delta only tests the sheath", "Joints have no losses", "It only works on paper cables", "Tan delta is an average over the whole length, so many metres of good cable can mask one defect" ], "answer": 3, "explanation": "Partial discharge testing with location can find individual defective accessories.", "ref": "IEEE 400.2" }, { "id": "MV509-041", "module": "MV-509", "level": "E", "region": "All", "question": "Under IEEE 400.2-2013, what mean tan delta at U0 for PE-based insulation moves a cable into the action required class?", "options": [ "Above 0.1 x 10^-3", "Above 50 x 10^-3", "Above 4 x 10^-3", "Above 5%" ], "answer": 1, "explanation": "Further study is 4 to 50 x 10^-3, and above 50 x 10^-3 needs action. Check the current edition.", "ref": "IEEE 400.2" }, { "id": "MV509-042", "module": "MV-509", "level": "E", "region": "All", "question": "What does a magnetic balance test on a three-limb transformer expect when voltage is applied to the centre phase?", "options": [ "One outer phase shows full voltage", "The outer phases each show about half the applied voltage", "No voltage appears on the outer phases", "The outer phases show twice the voltage" ], "answer": 1, "explanation": "The centre limb flux splits roughly equally between the outer limbs. A large imbalance suggests a core or winding fault.", "ref": "" }, { "id": "MV509-043", "module": "MV-509", "level": "E", "region": "All", "question": "After a winding resistance test with DC, why is a transformer demagnetised before energising?", "options": [ "To dry the oil", "To reduce inrush current, since remanent flux can cause very high inrush", "To reset the tap changer", "To cool the winding" ], "answer": 1, "explanation": "DC leaves residual magnetism in the core, which raises inrush and can trip protection.", "ref": "" }, { "id": "MV509-044", "module": "MV-509", "level": "E", "region": "All", "question": "For an IR test on equipment rated above 12 kV, what DC test voltage range does IEEE 43 suggest?", "options": [ "5,000 to 10,000 V", "15 to 25 kV", "500 to 1,000 V", "2,500 to 5,000 V" ], "answer": 0, "explanation": "IEEE 43 suggests 5 to 10 kV DC for windings rated above 12 kV.", "ref": "IEEE 43" }, { "id": "MV509-045", "module": "MV-509", "level": "E", "region": "All", "question": "What VLF withstand voltage at 3 U0 applies to a 12.7/22 kV cable?", "options": [ "About 66 kV rms", "About 12.7 kV rms", "About 22 kV rms", "About 38 kV rms" ], "answer": 3, "explanation": "U0 = 22/√3 = 12.7 kV, so 3 U0 = 38.1 kV rms.", "ref": "IEEE 400.2" }, { "id": "MV509-046", "module": "MV-509", "level": "E", "region": "All", "question": "What is the purpose of a hold point in an ITP?", "options": [ "It is an optional reminder", "It marks the end of the job", "It is where the client pays", "Work cannot continue past it until the named party has inspected or witnessed and released it" ], "answer": 3, "explanation": "Witness points can proceed if the party does not attend after notice, but hold points cannot.", "ref": "" }, { "id": "MV509-047", "module": "MV-509", "level": "E", "region": "KSA", "question": "For a 13.8 kV cable common in Saudi Arabia, what is 3 U0 for a VLF withstand?", "options": [ "About 41.4 kV", "About 8 kV", "About 23.9 kV", "About 13.8 kV" ], "answer": 2, "explanation": "U0 = 13.8/√3 = 7.97 kV, so 3 U0 = 23.9 kV rms. Use the SEC specified value.", "ref": "IEEE 400.2" }, { "id": "MV509-048", "module": "MV-509", "level": "E", "region": "NZ", "question": "In New Zealand, who sets the commissioning and test requirements for equipment connected to a lines company network?", "options": [ "Each EDB (lines company) in its network standards", "Transpower for all networks", "The retailer", "The local council" ], "answer": 0, "explanation": "EDBs such as Vector and Orion publish their own network standards and test requirements.", "ref": "" }, { "id": "MV509-049", "module": "MV-509", "level": "P", "region": "AU", "question": "Which standard gives inspection and testing guidelines for verifying LV installations in Australia and New Zealand?", "options": [ "AS/NZS 4836", "AS 2067", "AS/NZS 3008", "AS/NZS 3017" ], "answer": 3, "explanation": "AS/NZS 3017 covers verification tests such as continuity, IR, polarity and RCD tests before connection.", "ref": "AS/NZS 3017" }, { "id": "MV509-050", "module": "MV-509", "level": "P", "region": "NZ", "question": "Which AS/NZS standard covers periodic verification of existing electrical installations?", "options": [ "AS/NZS 3017", "AS/NZS 3012", "AS/NZS 3000", "AS/NZS 3019" ], "answer": 3, "explanation": "AS/NZS 3019 covers periodic inspection and testing, while AS/NZS 3017 covers new work.", "ref": "AS/NZS 3019" }, { "id": "MV510-001", "module": "MV-510", "level": "B", "region": "All", "question": "What is a switching program?", "options": [ "A written, numbered list of every switching operation, in order, with who does it and where", "A SCADA screen", "A relay setting file", "A maintenance budget" ], "answer": 0, "explanation": "It is prepared and checked in advance, then each step is carried out and confirmed with control.", "ref": "EN 50110-1" }, { "id": "MV510-002", "module": "MV-510", "level": "B", "region": "All", "question": "What is the correct core sequence for making MV equipment safe?", "options": [ "Permit, isolate, earth, prove dead", "Isolate, prove dead, earth, lock and tag, issue permit", "Prove dead, permit, isolate, earth", "Earth, isolate, prove dead, permit" ], "answer": 1, "explanation": "Never earth before proving dead, and never issue the permit before the earths are on.", "ref": "EN 50110-1" }, { "id": "MV510-003", "module": "MV-510", "level": "B", "region": "All", "question": "Why must you prove dead before applying earths?", "options": [ "To save time", "Earthing a live circuit creates a full short circuit that can injure the operator and damage equipment", "Earths do not work on live circuits", "It is only paperwork" ], "answer": 1, "explanation": "Proving dead first avoids closing an earth onto a live conductor.", "ref": "" }, { "id": "MV510-004", "module": "MV-510", "level": "B", "region": "All", "question": "Why is a voltage indicator tested before and after proving dead?", "options": [ "To prove it works, so a dead reading can be trusted", "To charge it", "It is not needed", "To reset the display" ], "answer": 0, "explanation": "This is the live-dead-live check. A failed indicator could show dead on a live circuit.", "ref": "IEC 61243-1" }, { "id": "MV510-005", "module": "MV-510", "level": "B", "region": "All", "question": "What does LOTO stand for?", "options": [ "Lock Out Tag Out", "Lock On Turn Off", "Line Open Test Only", "Load Over Trip Off" ], "answer": 0, "explanation": "Locks stop the isolation being changed, and tags show who isolated it and why.", "ref": "" }, { "id": "MV510-006", "module": "MV-510", "level": "B", "region": "All", "question": "In group LOTO, how should each worker protect themselves?", "options": [ "Fit a personal lock to a multi-lock hasp or group lock box", "Trust the supervisor's lock", "Use one shared tag", "Remove their lock at lunch" ], "answer": 0, "explanation": "The isolation cannot be removed until every worker has taken off their own lock.", "ref": "" }, { "id": "MV510-007", "module": "MV-510", "level": "B", "region": "All", "question": "What is a permit to work?", "options": [ "A trade licence", "A switching program", "A written document that confirms the equipment is isolated and earthed and defines the work and its limits", "A building permit" ], "answer": 2, "explanation": "It lists the isolation points and every earth applied for the work.", "ref": "" }, { "id": "MV510-008", "module": "MV-510", "level": "B", "region": "All", "question": "When can the earths for a job be removed?", "options": [ "At any time", "As soon as the work finishes", "After the permit is cancelled and everyone has left the work area", "Before the permit is cancelled" ], "answer": 2, "explanation": "Removing earths while the permit is live removes the protection the permit relies on.", "ref": "" }, { "id": "MV510-009", "module": "MV-510", "level": "B", "region": "All", "question": "Why close the normally open point before opening switches for planned work?", "options": [ "To back-feed substations beyond the work area so they stay on supply", "To earth the ring", "To trip the feeder", "To test the relays" ], "answer": 0, "explanation": "Only the section being worked on then loses supply.", "ref": "" }, { "id": "MV510-010", "module": "MV-510", "level": "B", "region": "All", "question": "What is the purpose of earthing the equipment on both sides of the work area?", "options": [ "To protect workers from accidental energisation and induced voltage from any direction", "To charge the cable", "To measure current", "To test the insulation" ], "answer": 0, "explanation": "The work area should sit between earths at every point of isolation.", "ref": "" }, { "id": "MV510-011", "module": "MV-510", "level": "B", "region": "All", "question": "Which device on an RMU shows whether each cable is live?", "options": [ "A Buchholz relay", "A voltage presence indicating system (VPIS)", "A tap changer", "A thermostat" ], "answer": 1, "explanation": "VPIS uses capacitive dividers and lamps on the panel front.", "ref": "IEC 61243-5" }, { "id": "MV510-012", "module": "MV-510", "level": "B", "region": "All", "question": "Before replacing a distribution transformer, which source is often missed?", "options": [ "The NOP", "The earth grid", "The VPIS", "LV back-feed from the LV board, another transformer or a generator" ], "answer": 3, "explanation": "The transformer can be made live from the LV side, so the LV side must be isolated and locked too.", "ref": "" }, { "id": "MV510-013", "module": "MV-510", "level": "B", "region": "All", "question": "What does an arc-rated (AR) PPE rating in cal/cm² describe?", "options": [ "Its cost", "Its weight", "Electrical insulation voltage", "The incident energy the clothing can withstand before a likely second-degree burn" ], "answer": 3, "explanation": "The arc rating (ATPV or EBT) must be at least the calculated incident energy.", "ref": "NFPA 70E" }, { "id": "MV510-014", "module": "MV-510", "level": "B", "region": "All", "question": "Which is the most effective way to reduce arc flash risk?", "options": [ "Wearing heavier PPE", "Opening doors while live", "Working faster", "Working de-energised, or operating remotely so people are away from the equipment" ], "answer": 3, "explanation": "PPE is the last line of defence. Removing exposure is the best control.", "ref": "NFPA 70E" }, { "id": "MV510-015", "module": "MV-510", "level": "B", "region": "All", "question": "What is a sanction for test?", "options": [ "A test certificate", "A document that allows testing which needs earths removed or voltage applied, under controlled conditions", "A fine", "A permit to energise permanently" ], "answer": 1, "explanation": "It is used where testing conflicts with the conditions of a permit to work.", "ref": "" }, { "id": "MV510-016", "module": "MV-510", "level": "B", "region": "All", "question": "Why is three-way communication used when giving switching instructions?", "options": [ "It replaces the switching program", "It is faster", "It is a legal formality only", "The receiver repeats the instruction back and the sender confirms, avoiding errors" ], "answer": 3, "explanation": "Repeat-back catches wrong switch numbers and locations before they are operated.", "ref": "" }, { "id": "MV510-017", "module": "MV-510", "level": "B", "region": "NZ", "question": "Which document sets the common switching and permit framework for New Zealand electricity networks?", "options": [ "AS/NZS 3000", "IEC 61936-1", "NZ Building Code", "EEA Safety Manual: Electricity Industry (SM-EI)" ], "answer": 3, "explanation": "The SM-EI is used across NZ lines companies, with each adding its own rules.", "ref": "" }, { "id": "MV510-018", "module": "MV-510", "level": "B", "region": "AU", "question": "Which national guideline underpins safe access rules for Australian network operators?", "options": [ "BS 7671", "ENA NENS 04", "IEEE 1584", "AS/NZS 3008" ], "answer": 1, "explanation": "ENA NENS 04 gives national guidelines for safe access to electrical and mechanical apparatus.", "ref": "" }, { "id": "MV510-019", "module": "MV-510", "level": "P", "region": "All", "question": "What are the five safety rules of EN 50110-1, in order?", "options": [ "Earth, disconnect, verify, secure, protect", "Permit, disconnect, earth, verify, test", "Verify, disconnect, earth, secure, protect", "Disconnect, secure against reconnection, verify absence of voltage, earth and short-circuit, protect against adjacent live parts" ], "answer": 3, "explanation": "These are often called the five golden rules.", "ref": "EN 50110-1" }, { "id": "MV510-020", "module": "MV-510", "level": "P", "region": "All", "question": "What does an earth switch making capacity class E2 under IEC 62271-102 mean?", "options": [ "It cannot be operated manually", "It is for LV only", "It can close onto a short circuit a set number of times (five for E2 at distribution voltages) and stay serviceable", "No making capacity" ], "answer": 2, "explanation": "E0 has no making capacity, E1 two operations and E2 five. A making rating protects the operator but is not a reason to skip proving dead.", "ref": "IEC 62271-102" }, { "id": "MV510-021", "module": "MV-510", "level": "P", "region": "All", "question": "Why are additional (drain) earths fitted at the point of work as well as the circuit main earths?", "options": [ "To control induced or residual voltage at the work location", "To speed up testing", "To reduce paperwork", "To replace the main earths" ], "answer": 0, "explanation": "Parallel circuits can induce voltage, and local earths keep the work point at earth potential.", "ref": "" }, { "id": "MV510-022", "module": "MV-510", "level": "P", "region": "All", "question": "Before cutting an MV cable that has been isolated and earthed, what extra step is common?", "options": [ "Remove the earths", "Nothing more", "Run a VLF test", "Identify the cable positively and spike it with a remote spiking tool" ], "answer": 3, "explanation": "Cable spiking proves the cable being cut is the dead one, since several cables may run in the same trench.", "ref": "" }, { "id": "MV510-023", "module": "MV-510", "level": "P", "region": "All", "question": "Before closing a normally open point, what should be confirmed?", "options": [ "Nothing", "Both feeders are in phase or from the same source, and loading and protection can take the closed ring", "The permit is issued", "The earths are on" ], "answer": 1, "explanation": "Closing across feeders out of phase or from different sources can cause large circulating currents.", "ref": "" }, { "id": "MV510-024", "module": "MV-510", "level": "P", "region": "All", "question": "A feeder trips on a cable fault. What must happen before re-closing the feeder breaker onto the remaining network?", "options": [ "Close the NOP onto the fault", "Locate and isolate the faulted section", "Nothing", "Earth the busbar" ], "answer": 1, "explanation": "Re-closing onto the fault would trip again and cause more damage.", "ref": "" }, { "id": "MV510-025", "module": "MV-510", "level": "P", "region": "All", "question": "At what incident energy is the arc flash boundary set under NFPA 70E?", "options": [ "8 cal/cm²", "1.2 cal/cm²", "4 cal/cm²", "40 cal/cm²" ], "answer": 1, "explanation": "1.2 cal/cm² is the onset of a second-degree burn on bare skin.", "ref": "NFPA 70E" }, { "id": "MV510-026", "module": "MV-510", "level": "P", "region": "All", "question": "An arc flash study gives 8 cal/cm² with a 0.4 s clearing time. If an energy reduction setting clears the fault in 0.1 s, roughly what is the new incident energy?", "options": [ "About 8 cal/cm²", "About 32 cal/cm²", "About 4 cal/cm²", "About 2 cal/cm²" ], "answer": 3, "explanation": "Incident energy is roughly proportional to arc duration, so a quarter of the time gives about a quarter of the energy.", "ref": "IEEE 1584" }, { "id": "MV510-027", "module": "MV-510", "level": "P", "region": "All", "question": "Which standard gives the calculation method for arc flash incident energy?", "options": [ "IEEE 1584", "IEEE 519", "IEC 60502-2", "IEC 60909" ], "answer": 0, "explanation": "IEEE 1584-2018 models arcing current and incident energy for 208 V to 15 kV equipment.", "ref": "IEEE 1584" }, { "id": "MV510-028", "module": "MV-510", "level": "P", "region": "All", "question": "What is the role of an authorised person in utility safety rules?", "options": [ "The client representative", "A person trained and appointed in writing to carry out specified switching and issue or receive specified documents", "A visitor", "Anyone on site" ], "answer": 1, "explanation": "Authorisation is limited to the equipment and tasks listed on the appointment.", "ref": "" }, { "id": "MV510-029", "module": "MV-510", "level": "P", "region": "All", "question": "Who should check a switching program before it is used?", "options": [ "A second competent person, independent of the writer", "Nobody", "The supplier", "The customer" ], "answer": 0, "explanation": "Independent checking catches wrong switch numbers and missed back-feeds.", "ref": "" }, { "id": "MV510-030", "module": "MV-510", "level": "P", "region": "GCC", "question": "For utility-owned 11 kV equipment in a GCC building substation, who controls switching?", "options": [ "The consultant", "The utility, through its control centre and its own authorised staff", "The facility manager", "The building contractor" ], "answer": 1, "explanation": "Contractors work under the utility permits for utility-owned equipment.", "ref": "" }, { "id": "MV510-031", "module": "MV-510", "level": "P", "region": "AU", "question": "In Victoria, which code of practice sets electrical safety rules for distribution businesses?", "options": [ "The Red Book", "AS/NZS 3000", "The Blue Book", "SM-EI" ], "answer": 2, "explanation": "The Blue Book (Code of Practice on Electrical Safety for the Distribution Businesses in Victoria) covers access and switching.", "ref": "" }, { "id": "MV510-032", "module": "MV-510", "level": "P", "region": "NZ", "question": "Which regulations set the main legal safety framework for electrical work in New Zealand?", "options": [ "Building Act only", "Resource Management Act", "Electricity (Safety) Regulations 2010", "Health Act" ], "answer": 2, "explanation": "They reference standards and codes of practice, with WorkSafe as regulator.", "ref": "" }, { "id": "MV510-033", "module": "MV-510", "level": "P", "region": "All", "question": "Why are switching operations on MV switchgear increasingly done remotely or with remote racking?", "options": [ "Because local operation is banned everywhere", "To save cable", "To speed up the program", "To keep the operator outside the arc flash boundary" ], "answer": 3, "explanation": "Distance is one of the most effective arc flash controls.", "ref": "NFPA 70E" }, { "id": "MV510-034", "module": "MV-510", "level": "E", "region": "All", "question": "Can a permit to work and a sanction for test be in force on the same equipment at the same time under typical UK-style rules?", "options": [ "No, the permit is cancelled or suspended before the sanction for test is issued", "Only if the client agrees", "Only at night", "Yes, always" ], "answer": 0, "explanation": "The two documents define conflicting conditions, so only one is in force at a time.", "ref": "" }, { "id": "MV510-035", "module": "MV-510", "level": "E", "region": "All", "question": "Why might a cable that has been isolated and earthed at both ends still be dangerous during jointing?", "options": [ "Cable capacitance stores charge forever", "It cannot be", "The VPIS is wrong", "Induced voltage from parallel live circuits and step or touch voltage during faults on nearby circuits" ], "answer": 3, "explanation": "Additional earths and bonding at the work point control these risks.", "ref": "" }, { "id": "MV510-036", "module": "MV-510", "level": "E", "region": "All", "question": "What is the typical IEEE 1584-2018 working distance for 15 kV class switchgear?", "options": [ "914 mm", "455 mm", "2,000 mm", "610 mm" ], "answer": 0, "explanation": "914 mm (36 in) is used for MV switchgear. LV switchgear uses 610 mm.", "ref": "IEEE 1584" }, { "id": "MV510-037", "module": "MV-510", "level": "E", "region": "All", "question": "Why does NFPA 70E say arc-rated PPE must not be the first choice of control?", "options": [ "It is expensive", "It is only for LV", "PPE does not exist above 8 cal/cm²", "The hierarchy of controls puts elimination and engineering controls above PPE" ], "answer": 3, "explanation": "Elimination, substitution, engineering and administrative controls come first.", "ref": "NFPA 70E" }, { "id": "MV510-038", "module": "MV-510", "level": "E", "region": "All", "question": "A switching program says close the earth switch on RMU circuit 2, but the VPIS shows voltage on that cable. What should the operator do?", "options": [ "Open the feeder at the primary without telling control", "Close it, since the switch is fault-make rated", "Stop, report to control and investigate the source before any further step", "Remove the VPIS" ], "answer": 2, "explanation": "An unexpected live indication means the isolation is incomplete, perhaps from a back-feed or the wrong cable.", "ref": "" }, { "id": "MV510-039", "module": "MV-510", "level": "E", "region": "All", "question": "Why is the restoration part of a switching program as important as the isolation part?", "options": [ "It is only paperwork", "It is done by the customer", "Earths left on or steps done out of order can cause faults on re-energisation", "It is not" ], "answer": 2, "explanation": "Re-energising with an earth still applied causes a full short circuit.", "ref": "" }, { "id": "MV510-040", "module": "MV-510", "level": "E", "region": "All", "question": "What is the main purpose of a limitation of access document?", "options": [ "To energise equipment", "To control work near, but not on, electrical equipment where a permit to work is not suitable", "To isolate HV equipment", "To test relays" ], "answer": 1, "explanation": "It defines the work and the hazards for activities such as civil work near equipment.", "ref": "" }, { "id": "MV510-041", "module": "MV-510", "level": "E", "region": "All", "question": "Why must an LV generator or UPS that can feed back through a transformer be in the isolation plan?", "options": [ "A back-feed through the transformer steps the LV up to full MV on the \"isolated\" side", "It cannot feed back", "It only affects LV", "It improves power factor" ], "answer": 0, "explanation": "A transformer works both ways, so 400 V fed in can produce 11 kV on the HV terminals.", "ref": "" }, { "id": "MV510-042", "module": "MV-510", "level": "E", "region": "GCC", "question": "In GCC building substations, why is it important to know which RMU and transformer belong to the utility and which to the consumer?", "options": [ "Only for painting", "It only affects billing", "There is no difference", "Operation and permits for each part follow different owners' safety rules and authorisations" ], "answer": 3, "explanation": "Consumer staff must not operate utility equipment and vice versa without the right authorisation.", "ref": "" }, { "id": "MV510-043", "module": "MV-510", "level": "E", "region": "KSA", "question": "In Saudi Arabia, which body's safety rules and permits govern work on its 13.8 kV distribution network?", "options": [ "Transpower", "Saudi Electricity Company (SEC)", "DEWA", "KAHRAMAA" ], "answer": 1, "explanation": "SEC operates the national distribution network and sets the safety rules for work on it.", "ref": "" }, { "id": "MV510-044", "module": "MV-510", "level": "E", "region": "Asia", "question": "In Malaysia, which utility's rules govern switching on its MV distribution network?", "options": [ "TNB", "PLN", "SP Group", "CLP" ], "answer": 0, "explanation": "Tenaga Nasional Berhad operates the network in Peninsular Malaysia and sets the safety rules and authorisations for switching on it.", "ref": "" }, { "id": "MV510-045", "module": "MV-510", "level": "E", "region": "All", "question": "Two crews need work on the same isolated cable section. How is this usually handled under a permit system?", "options": [ "One permit and nobody signs", "The second crew waits outside but works anyway", "They share a verbal agreement", "Each crew works under a permit or is signed onto the permit, and each fits a personal lock" ], "answer": 3, "explanation": "Every person must be covered by the safety document and their own lock.", "ref": "" }, { "id": "MV510-046", "module": "MV-510", "level": "E", "region": "All", "question": "What should happen if a step in the switching program cannot be done as written, for example a switch label does not match?", "options": [ "Skip the step", "Stop and refer back to control, so the program can be amended and rechecked", "Do the next step first", "Improvise" ], "answer": 1, "explanation": "Deviating from a checked program removes the protection that checking gives.", "ref": "" }, { "id": "MV510-047", "module": "MV-510", "level": "E", "region": "All", "question": "Why is incident energy often higher on the line side of a main LV breaker than on its load side?", "options": [ "It is not", "A fault on the line side is cleared by upstream MV protection, which is usually slower", "The voltage is higher", "The cable is shorter" ], "answer": 1, "explanation": "Long clearing times on the transformer HV protection give high arc energy at the LV incomer terminals.", "ref": "IEEE 1584" }, { "id": "MV511-001", "module": "MV-511", "level": "B", "region": "All", "question": "Why does a utility ask for a substation on the developer's land?", "options": [ "For decoration", "To store cables", "For metering only", "When the building load is too large for an LV connection from the street network" ], "answer": 3, "explanation": "Large loads need a dedicated transformer close to the load.", "ref": "" }, { "id": "MV511-002", "module": "MV-511", "level": "B", "region": "All", "question": "What is usually the first step in getting a new MV connection?", "options": [ "Energisation", "Submitting a load application with the maximum demand estimate", "Ordering the meters", "Installing the transformer" ], "answer": 1, "explanation": "The utility uses the load application to decide the connection conditions.", "ref": "" }, { "id": "MV511-003", "module": "MV-511", "level": "B", "region": "All", "question": "What is the utility's reply to a load application often called?", "options": [ "A completion certificate", "A connection offer or supply conditions", "A permit to work", "A test report" ], "answer": 1, "explanation": "It sets the substation size, number of transformers, cable route and fees.", "ref": "" }, { "id": "MV511-004", "module": "MV-511", "level": "B", "region": "All", "question": "Which item is most often on the critical path for an MV connection?", "options": [ "Ordering LV lamps", "Painting the corridor", "Landscaping", "Substation room completion and handover to the utility" ], "answer": 3, "explanation": "The utility cannot install the RMU and transformers until the room is ready.", "ref": "" }, { "id": "MV511-005", "module": "MV-511", "level": "B", "region": "All", "question": "What is the most common cause of delay in utility design approvals?", "options": [ "The colour of drawings", "Weather", "Too many copies", "Incomplete or non-compliant submissions that come back with comments" ], "answer": 3, "explanation": "Each resubmission cycle can add weeks.", "ref": "" }, { "id": "MV511-006", "module": "MV-511", "level": "B", "region": "All", "question": "What does a critical path show?", "options": [ "The route of the cable", "The cheapest cable route", "The risk register", "The longest chain of dependent activities that sets the end date" ], "answer": 3, "explanation": "Any delay on the critical path delays energisation.", "ref": "PMI PMBOK" }, { "id": "MV511-007", "module": "MV-511", "level": "B", "region": "All", "question": "What is total float?", "options": [ "How long an activity can slip without delaying the project end date", "The time to energise", "The cable length spare", "The cost buffer" ], "answer": 0, "explanation": "Critical path activities have zero total float.", "ref": "PMI PMBOK" }, { "id": "MV511-008", "module": "MV-511", "level": "B", "region": "All", "question": "When should the substation location and size be agreed with the utility?", "options": [ "After building handover", "Early, at concept design", "At energisation", "Never" ], "answer": 1, "explanation": "Late changes after the architecture is frozen are expensive and slow.", "ref": "" }, { "id": "MV511-009", "module": "MV-511", "level": "B", "region": "All", "question": "What usually happens just before the utility energises a new substation?", "options": [ "Concept design", "Tendering", "Load application", "Final pre-energisation inspection and witnessed tests" ], "answer": 3, "explanation": "Tests and records must be accepted before the utility energises and meters the supply.", "ref": "" }, { "id": "MV511-010", "module": "MV-511", "level": "B", "region": "GCC", "question": "Which utility handles new electricity connections in Dubai?", "options": [ "ADDC", "SEWA", "DEWA", "KAHRAMAA" ], "answer": 2, "explanation": "Dubai Electricity and Water Authority runs the connection process in Dubai.", "ref": "" }, { "id": "MV511-011", "module": "MV-511", "level": "B", "region": "GCC", "question": "Which utility handles distribution connections in Qatar?", "options": [ "SEC", "EWA", "KAHRAMAA", "DEWA" ], "answer": 2, "explanation": "KAHRAMAA (Qatar General Electricity and Water Corporation) handles connections in Qatar.", "ref": "" }, { "id": "MV511-012", "module": "MV-511", "level": "B", "region": "KSA", "question": "Which company handles MV distribution connections across most of Saudi Arabia?", "options": [ "ADDC", "DEWA", "SEC", "MEW" ], "answer": 2, "explanation": "Saudi Electricity Company operates the distribution network across the Kingdom.", "ref": "" }, { "id": "MV511-013", "module": "MV-511", "level": "B", "region": "NZ", "question": "In New Zealand, what is the business that owns local distribution networks called?", "options": [ "A TSO", "An EDB (electricity distribution business), or lines company", "A retailer", "A DNSP" ], "answer": 1, "explanation": "There are around 29 EDBs, such as Vector, Orion and Powerco.", "ref": "" }, { "id": "MV511-014", "module": "MV-511", "level": "B", "region": "AU", "question": "In Australia, what is the business that owns local distribution networks called?", "options": [ "An ASP", "An EDB", "A DNSP (distribution network service provider)", "A TNSP only" ], "answer": 2, "explanation": "Examples include Ausgrid, Energex and Western Power.", "ref": "" }, { "id": "MV511-015", "module": "MV-511", "level": "B", "region": "All", "question": "What does a substation room approval check?", "options": [ "The LV load schedule only", "Only the paint colour", "Room size, access, ventilation, doors, trenches, earthing and fire separation against the utility standard", "Only the lighting" ], "answer": 2, "explanation": "The room must match the utility standard before equipment is installed.", "ref": "" }, { "id": "MV511-016", "module": "MV-511", "level": "B", "region": "All", "question": "Why is the cable route important in the approval process?", "options": [ "It sets the tariff", "It changes the voltage", "It is not", "It may cross roads and other services and need permits and wayleaves that take time" ], "answer": 3, "explanation": "Road crossings and third party land often need their own approvals.", "ref": "" }, { "id": "MV511-017", "module": "MV-511", "level": "B", "region": "All", "question": "What does energisation mean in the connection workflow?", "options": [ "Ordering the transformer", "Design approval", "The utility connects the new substation to the live network and supply starts", "Room handover" ], "answer": 2, "explanation": "It is normally the last utility stage, followed by metering and supply.", "ref": "" }, { "id": "MV511-018", "module": "MV-511", "level": "P", "region": "All", "question": "Activities: A (4 weeks), then B (6 weeks) and C (3 weeks) in parallel after A, then D (5 weeks) after both. What is the project duration?", "options": [ "12 weeks", "15 weeks", "13 weeks", "18 weeks" ], "answer": 1, "explanation": "The longest path is A + B + D = 4 + 6 + 5 = 15 weeks.", "ref": "PMI PMBOK" }, { "id": "MV511-019", "module": "MV-511", "level": "P", "region": "All", "question": "In the same network (A 4, B 6, C 3, D 5, with B and C in parallel), what is the total float of C?", "options": [ "3 weeks", "0 weeks", "5 weeks", "6 weeks" ], "answer": 0, "explanation": "C can finish 3 weeks later before it delays D, because B takes 6 weeks against 3.", "ref": "PMI PMBOK" }, { "id": "MV511-020", "module": "MV-511", "level": "P", "region": "All", "question": "A non-critical activity with 4 weeks of float slips by 2 weeks. What happens to the energisation date?", "options": [ "It slips 2 weeks", "It does not change, but float drops to 2 weeks", "It moves earlier", "It slips 4 weeks" ], "answer": 1, "explanation": "Only slips greater than the float delay the end date.", "ref": "PMI PMBOK" }, { "id": "MV511-021", "module": "MV-511", "level": "P", "region": "All", "question": "Starting substation civil works before design approval is an example of...", "options": [ "Fast tracking, which saves time but risks rework", "Resource levelling", "Crashing", "Float" ], "answer": 0, "explanation": "Overlapping stages saves time but rework is possible if the approved design changes.", "ref": "PMI PMBOK" }, { "id": "MV511-022", "module": "MV-511", "level": "P", "region": "All", "question": "Which documents are typically in an MV substation design submission?", "options": [ "The tender documents", "Only the architectural elevations", "Load schedule, SLD, room layout and sections, earthing layout, cable route and site plan", "The LV lighting layouts only" ], "answer": 2, "explanation": "Utilities list exact requirements, but these are the core items.", "ref": "" }, { "id": "MV511-023", "module": "MV-511", "level": "P", "region": "All", "question": "Why are long lead items such as transformers tracked early in the programme?", "options": [ "They need no approval", "They are installed last", "Delivery can take months and can move onto the critical path", "They are cheap" ], "answer": 2, "explanation": "Late orders often become the controlling activity for energisation.", "ref": "" }, { "id": "MV511-024", "module": "MV-511", "level": "P", "region": "GCC", "question": "In Dubai, what other authority approval is usually needed for the substation room besides DEWA?", "options": [ "RTA only", "Dubai Civil Defence (fire safety)", "Dubai Customs", "DHA" ], "answer": 1, "explanation": "Civil Defence approval covers fire separation and protection of the room.", "ref": "" }, { "id": "MV511-025", "module": "MV-511", "level": "P", "region": "GCC", "question": "In Dubai, which authority issues the NOC for cable works within the road right of way?", "options": [ "RTA", "DEWA water division", "DHA", "DCD" ], "answer": 0, "explanation": "Roads and Transport Authority permits are needed for works in road reserves.", "ref": "" }, { "id": "MV511-026", "module": "MV-511", "level": "P", "region": "GCC", "question": "In many GCC utilities, which items does the utility often supply and install in a consumer substation room?", "options": [ "The architectural finishes", "The fire alarm system", "The 11 kV RMU and distribution transformers", "The building LV final circuits" ], "answer": 2, "explanation": "The developer usually provides the room and pays connection charges. Check each utility's current rules.", "ref": "" }, { "id": "MV511-027", "module": "MV-511", "level": "P", "region": "AU", "question": "Which part of the National Electricity Rules covers connections for retail customers to distribution networks?", "options": [ "Chapter 7", "Chapter 3", "Chapter 10", "Chapter 5A" ], "answer": 3, "explanation": "Chapter 5A sets the connection framework for retail customers.", "ref": "National Electricity Rules" }, { "id": "MV511-028", "module": "MV-511", "level": "P", "region": "AU", "question": "In New South Wales, which ASP level covers the design of contestable network works?", "options": [ "Level 2", "Level 4", "Level 1", "Level 3" ], "answer": 3, "explanation": "Level 1 constructs, Level 2 does service and connection work, Level 3 designs.", "ref": "" }, { "id": "MV511-029", "module": "MV-511", "level": "P", "region": "NZ", "question": "What is the unique identifier for a connection point used by NZ retailers and the registry?", "options": [ "ICP number", "PoS code", "MPAN", "NMI" ], "answer": 0, "explanation": "The Installation Control Point (ICP) number identifies each connection in the NZ registry.", "ref": "" }, { "id": "MV511-030", "module": "MV-511", "level": "P", "region": "AU", "question": "What is the unique identifier for a connection point in the Australian NEM?", "options": [ "ICP", "MPRN", "NMI (National Metering Identifier)", "Account number" ], "answer": 2, "explanation": "Each connection point has a NMI, used by retailers and AEMO.", "ref": "" }, { "id": "MV511-031", "module": "MV-511", "level": "P", "region": "All", "question": "Why does a weekly look-ahead with the utility help the connection programme?", "options": [ "It finds approval, witness and inspection bookings early, so they do not delay hold points", "It is not needed", "It sets the tariff", "It replaces the critical path" ], "answer": 0, "explanation": "Utility witness slots are often booked weeks ahead.", "ref": "" }, { "id": "MV511-032", "module": "MV-511", "level": "P", "region": "Asia", "question": "In Singapore, which body regulates the electricity market while SP Group handles grid connections?", "options": [ "TNB", "CLP", "EMA (Energy Market Authority)", "DEWA" ], "answer": 2, "explanation": "EMA regulates, and SP Group runs the network and connection process.", "ref": "" }, { "id": "MV511-033", "module": "MV-511", "level": "E", "region": "All", "question": "A design resubmission adds 4 weeks to an activity on the critical path, and a parallel path has 3 weeks of float. How much does energisation slip?", "options": [ "7 weeks", "0 weeks", "4 weeks", "1 week" ], "answer": 2, "explanation": "The delayed activity is on the critical path itself, so the full 4 weeks passes to the end date. The float on the other path does not help.", "ref": "PMI PMBOK" }, { "id": "MV511-034", "module": "MV-511", "level": "E", "region": "All", "question": "A path has 3 weeks of total float. One of its activities slips 5 weeks. How much does the end date move?", "options": [ "0 weeks", "5 weeks", "2 weeks", "8 weeks" ], "answer": 2, "explanation": "The first 3 weeks use up the float, and the remaining 2 weeks delay the end date. That path becomes critical.", "ref": "PMI PMBOK" }, { "id": "MV511-035", "module": "MV-511", "level": "E", "region": "All", "question": "What is the difference between total float and free float?", "options": [ "Free float is always larger", "Total float applies only to milestones", "Free float is the delay possible without delaying the next activity, total float without delaying the project end", "They are the same" ], "answer": 2, "explanation": "Free float can be zero while total float is positive.", "ref": "PMI PMBOK" }, { "id": "MV511-036", "module": "MV-511", "level": "E", "region": "All", "question": "Why does crashing an activity that is not on the critical path not bring energisation forward?", "options": [ "The end date is set by the critical path, so shortening non-critical work only adds float", "Crashing is not allowed", "It increases float on the critical path", "It always does" ], "answer": 0, "explanation": "Only shortening critical activities can shorten the project.", "ref": "PMI PMBOK" }, { "id": "MV511-037", "module": "MV-511", "level": "E", "region": "All", "question": "Which interface risk most often delays a utility installing its RMU even when the room is built?", "options": [ "LV lighting not dimmable", "Room not formally handed over: missing access, doors, trench covers, earthing or a clear dust-free area", "Too many cable trays", "Wrong paint colour" ], "answer": 1, "explanation": "Utilities inspect the room against their standard before accepting it.", "ref": "" }, { "id": "MV511-038", "module": "MV-511", "level": "E", "region": "All", "question": "Why should the consultant confirm the utility's current requirements rather than rely on a previous project?", "options": [ "It saves fees", "Utility standards, forms, fees and portal steps change, and old submissions can be rejected", "Utilities never change", "It is optional" ], "answer": 1, "explanation": "Rejection for using outdated templates is a common delay.", "ref": "" }, { "id": "MV511-039", "module": "MV-511", "level": "E", "region": "GCC", "question": "Which Abu Dhabi distribution company serves Abu Dhabi city, as distinct from Al Ain?", "options": [ "SEWA", "AADC", "FEWA", "ADDC" ], "answer": 3, "explanation": "ADDC serves Abu Dhabi and AADC serves the Al Ain region, with both now under TAQA Distribution.", "ref": "" }, { "id": "MV511-040", "module": "MV-511", "level": "E", "region": "AU", "question": "In NSW, what certificate must a licensed electrician submit after electrical installation work?", "options": [ "CCEW (Certificate of Compliance for Electrical Work)", "NOC", "ESC", "CoC" ], "answer": 0, "explanation": "The CCEW is lodged with the distributor and Fair Trading.", "ref": "" }, { "id": "MV511-041", "module": "MV-511", "level": "E", "region": "NZ", "question": "Which documents are issued for prescribed electrical work in New Zealand before connection?", "options": [ "Certificate of Compliance (CoC) and Electrical Safety Certificate (ESC)", "NOC only", "Building consent only", "CCEW only" ], "answer": 0, "explanation": "High-risk work also needs a Record of Inspection by an inspector.", "ref": "" }, { "id": "MV511-042", "module": "MV-511", "level": "E", "region": "All", "question": "A utility witness test is a hold point. The test fails and needs re-booking with a 2 week lead time. On the critical path, what is the minimum delay?", "options": [ "It depends only on weather", "At least 2 weeks plus the repair time", "Half a week", "None" ], "answer": 1, "explanation": "The repair must be done and the witness re-booked before the next stage can start.", "ref": "" }, { "id": "MV511-043", "module": "MV-511", "level": "E", "region": "All", "question": "Why is a resubmission loop modelled as a separate activity in the programme rather than hidden in design time?", "options": [ "It looks better", "It makes the risk visible and lets the team see its effect on the critical path", "It reduces fees", "Utilities require it" ], "answer": 1, "explanation": "Planning realistic review cycles avoids optimistic energisation dates.", "ref": "PMI PMBOK" }, { "id": "MV511-044", "module": "MV-511", "level": "E", "region": "All", "question": "Where both MV and LV metering are possible, what decides the metering point for a large consumer?", "options": [ "The contractor's preference", "The cable size only", "The paint finish", "The utility's tariff and connection rules, often based on load size and who owns the transformer" ], "answer": 3, "explanation": "Ownership of the transformer and the tariff class usually set where the meter goes.", "ref": "" }, { "id": "MV511-045", "module": "MV-511", "level": "E", "region": "All", "question": "What does a contestable works model change in the connection workflow?", "options": [ "The customer's accredited contractor designs and builds the network extension, and the utility audits and takes it over", "The utility does everything at no cost", "The customer owns the grid", "Nothing" ], "answer": 0, "explanation": "This is used in NSW, Victoria and other places, with handover at completion.", "ref": "" }, { "id": "MV511-046", "module": "MV-511", "level": "E", "region": "All", "question": "Why are third party cable route wayleaves often the hardest item to plan?", "options": [ "They are quick", "Agreements with landowners and other authorities have uncertain timelines outside the project's control", "They need no drawings", "They are only for LV" ], "answer": 1, "explanation": "Uncertain external durations are a key schedule risk.", "ref": "" }, { "id": "MV511-047", "module": "MV-511", "level": "E", "region": "All", "question": "What is the main reason to agree an energisation date with the utility well in advance?", "options": [ "To change the voltage", "To avoid testing", "Utility outage and switching slots are planned ahead, and the connection may need a planned outage on the existing network", "To fix the tariff" ], "answer": 2, "explanation": "Connecting a new substation into a ring often needs switching and a planned outage.", "ref": "" }, { "id": "MV512-001", "module": "MV-512", "level": "B", "region": "All", "question": "What causes harmonics in a building supply?", "options": [ "Resistive heaters", "Copper cables", "Non-linear loads such as drives, UPS rectifiers, LED drivers and IT power supplies", "Incandescent lamps" ], "answer": 2, "explanation": "These loads draw current in pulses instead of a smooth sine wave.", "ref": "" }, { "id": "MV512-002", "module": "MV-512", "level": "B", "region": "All", "question": "What does THD stand for?", "options": [ "Total Harmonic Distortion", "Thermal Heat Dissipation", "Transformer High Demand", "Three-phase Harmonic Detection" ], "answer": 0, "explanation": "THD compares the harmonic content to the fundamental.", "ref": "IEEE 519" }, { "id": "MV512-003", "module": "MV-512", "level": "B", "region": "All", "question": "How is current THD calculated?", "options": [ "I1 / Irms", "√(Σ Ih²) / I1", "Ipeak / Irms", "Sum of all harmonics divided by I1" ], "answer": 1, "explanation": "It is the rms of the harmonic currents divided by the fundamental current.", "ref": "IEEE 519" }, { "id": "MV512-004", "module": "MV-512", "level": "B", "region": "All", "question": "Which harmonics do six-pulse drives mainly produce?", "options": [ "3rd only", "2nd and 4th", "5th and 7th", "Even harmonics only" ], "answer": 2, "explanation": "Six-pulse rectifiers produce h = 6k ± 1: 5, 7, 11, 13 and so on.", "ref": "" }, { "id": "MV512-005", "module": "MV-512", "level": "B", "region": "All", "question": "Why do triplen harmonics overload the neutral?", "options": [ "They are DC", "They flow only in phase A", "They cancel", "They are in phase in all three phases, so they add in the neutral" ], "answer": 3, "explanation": "3rd, 9th and 15th harmonics are zero sequence.", "ref": "" }, { "id": "MV512-006", "module": "MV-512", "level": "B", "region": "All", "question": "What is the crest factor of a pure sine wave?", "options": [ "1.414", "2.0", "1.0", "1.73" ], "answer": 0, "explanation": "Crest factor = peak / rms = √2 for a sine.", "ref": "" }, { "id": "MV512-007", "module": "MV-512", "level": "B", "region": "All", "question": "What is the IEEE 519 voltage THD limit at the point of common coupling for systems from 1 kV to 69 kV?", "options": [ "10%", "3%", "5%", "8%" ], "answer": 2, "explanation": "Up to 1 kV the limit is 8%, and from 1 to 69 kV it is 5%.", "ref": "IEEE 519" }, { "id": "MV512-008", "module": "MV-512", "level": "B", "region": "All", "question": "What is the IEEE 519 voltage THD limit at the PCC for systems up to 1 kV?", "options": [ "5%", "8%", "12%", "3%" ], "answer": 1, "explanation": "8% applies to systems at 1 kV and below.", "ref": "IEEE 519" }, { "id": "MV512-009", "module": "MV-512", "level": "B", "region": "All", "question": "What is the formula for the capacitor kvar needed to improve power factor?", "options": [ "Qc = P / PF", "Qc = S x PF", "Qc = P x (cos φ1 - cos φ2)", "Qc = P x (tan φ1 - tan φ2)" ], "answer": 3, "explanation": "φ1 and φ2 are the angles for the existing and target power factor.", "ref": "" }, { "id": "MV512-010", "module": "MV-512", "level": "B", "region": "All", "question": "What is a K-rated transformer designed for?", "options": [ "Outdoor use", "Supplying non-linear loads with harmonic currents without overheating", "Lower cost", "Higher voltage" ], "answer": 1, "explanation": "K-factor reflects the extra eddy current heating from harmonics.", "ref": "" }, { "id": "MV512-011", "module": "MV-512", "level": "B", "region": "All", "question": "What is a detuned capacitor bank?", "options": [ "A capacitor bank with series reactors that tune it below the lowest major harmonic", "A bank without control", "A bank that is switched off", "A bank with no fuses" ], "answer": 0, "explanation": "This stops the bank resonating with the network at the 5th and 7th harmonics.", "ref": "" }, { "id": "MV512-012", "module": "MV-512", "level": "B", "region": "All", "question": "What frequency does a 7% detuned reactor tune a capacitor bank to on a 50 Hz system?", "options": [ "134 Hz", "189 Hz", "50 Hz", "250 Hz" ], "answer": 1, "explanation": "f = 50 / √0.07 = 189 Hz, about 3.78 times fundamental.", "ref": "" }, { "id": "MV512-013", "module": "MV-512", "level": "B", "region": "All", "question": "What frequency does a 14% detuned reactor tune a bank to on a 50 Hz system?", "options": [ "150 Hz", "134 Hz", "189 Hz", "210 Hz" ], "answer": 1, "explanation": "f = 50 / √0.14 = 134 Hz, below the 3rd harmonic at 150 Hz.", "ref": "" }, { "id": "MV512-014", "module": "MV-512", "level": "B", "region": "All", "question": "What does flicker describe?", "options": [ "Earth leakage", "Visible changes in light output caused by repeated voltage fluctuations", "Harmonic heating", "Frequency drift" ], "answer": 1, "explanation": "Arc furnaces, welders and large motors starting often cause flicker.", "ref": "IEC 61000-4-15" }, { "id": "MV512-015", "module": "MV-512", "level": "B", "region": "All", "question": "What is an active harmonic filter?", "options": [ "A tuned LC branch", "A larger cable", "A surge arrester", "A power electronic device that injects currents to cancel measured harmonics" ], "answer": 3, "explanation": "It adapts to changing loads and does not create resonance like a fixed bank.", "ref": "" }, { "id": "MV512-016", "module": "MV-512", "level": "B", "region": "All", "question": "Which IEC series covers electromagnetic compatibility, including harmonics and flicker?", "options": [ "IEC 62271", "IEC 61000", "IEC 60364", "IEC 60909" ], "answer": 1, "explanation": "For example IEC 61000-2-4, 61000-3-6 and 61000-4-30.", "ref": "IEC 61000" }, { "id": "MV512-017", "module": "MV-512", "level": "B", "region": "KSA", "question": "In Saudi Arabia, at what frequency does the 5th harmonic sit?", "options": [ "250 Hz", "350 Hz", "420 Hz", "300 Hz" ], "answer": 3, "explanation": "The SEC grid runs at 60 Hz, so the 5th harmonic is 5 x 60 = 300 Hz.", "ref": "" }, { "id": "MV512-018", "module": "MV-512", "level": "B", "region": "All", "question": "What does a power factor penalty in a utility tariff encourage?", "options": [ "Correcting reactive power locally so less kvar is drawn from the grid", "More harmonics", "Larger transformers", "Higher kW" ], "answer": 0, "explanation": "Utilities set minimum power factors in their regulations or tariffs.", "ref": "" }, { "id": "MV512-019", "module": "MV-512", "level": "B", "region": "GCC", "question": "Why are detuned capacitor banks common in GCC buildings?", "options": [ "They are cheaper than plain banks", "Large chiller plants with VFDs create harmonics that could resonate with plain capacitor banks", "Utilities ban capacitors", "There are no harmonics there" ], "answer": 1, "explanation": "Detuning protects the capacitors and avoids amplifying 5th and 7th harmonics.", "ref": "" }, { "id": "MV512-020", "module": "MV-512", "level": "P", "region": "All", "question": "A load currents are I1 = 100 A, I5 = 20 A, I7 = 14 A, I11 = 9 A and I13 = 7 A. What is the current THD?", "options": [ "20%", "27%", "36%", "50%" ], "answer": 1, "explanation": "√(20² + 14² + 9² + 7²) = √726 = 26.9 A, so THD = 26.9%.", "ref": "IEEE 519" }, { "id": "MV512-021", "module": "MV-512", "level": "P", "region": "All", "question": "How does TDD differ from THD in IEEE 519?", "options": [ "They are identical", "TDD ignores the 5th", "TDD uses voltage", "TDD divides the harmonic current by the maximum demand load current IL instead of the present fundamental" ], "answer": 3, "explanation": "TDD avoids light load readings looking alarmingly high.", "ref": "IEEE 519" }, { "id": "MV512-022", "module": "MV-512", "level": "P", "region": "All", "question": "Harmonic current is 60 A rms and the maximum demand current IL is 1,000 A. What is the TDD?", "options": [ "60%", "6%", "0.6%", "16.7%" ], "answer": 1, "explanation": "TDD = 60 / 1,000 = 6%.", "ref": "IEEE 519" }, { "id": "MV512-023", "module": "MV-512", "level": "P", "region": "All", "question": "Under IEEE 519-2022, what is the TDD limit for systems from 120 V to 69 kV where ISC/IL is below 20?", "options": [ "5%", "8%", "20%", "12%" ], "answer": 0, "explanation": "The limit rises to 8%, 12%, 15% and 20% as the short-circuit ratio increases.", "ref": "IEEE 519" }, { "id": "MV512-024", "module": "MV-512", "level": "P", "region": "All", "question": "How much kvar is needed to raise 800 kW from 0.75 to 0.95 power factor?", "options": [ "About 443 kvar", "About 600 kvar", "About 800 kvar", "About 250 kvar" ], "answer": 0, "explanation": "tan(acos 0.75) = 0.882 and tan(acos 0.95) = 0.329. 800 x 0.553 = 443 kvar.", "ref": "" }, { "id": "MV512-025", "module": "MV-512", "level": "P", "region": "All", "question": "How much kvar is needed to raise 500 kW from 0.80 to 0.95 power factor?", "options": [ "About 211 kvar", "About 500 kvar", "About 125 kvar", "About 375 kvar" ], "answer": 0, "explanation": "500 x (0.750 - 0.329) = 211 kvar.", "ref": "" }, { "id": "MV512-026", "module": "MV-512", "level": "P", "region": "All", "question": "What is the approximate parallel resonance order of a capacitor bank with the supply?", "options": [ "√(Ssc / Qc)", "Ssc x Qc", "Ssc / Qc", "Qc / Ssc" ], "answer": 0, "explanation": "hr = √(Ssc/Qc), where Ssc is the short-circuit power at the bank.", "ref": "" }, { "id": "MV512-027", "module": "MV-512", "level": "P", "region": "All", "question": "A 1,500 kVA, 6% impedance transformer feeds a 500 kvar plain capacitor bank. Ignoring the source impedance, near which harmonic is the parallel resonance?", "options": [ "3rd", "5th", "7th", "13th" ], "answer": 2, "explanation": "Ssc ≈ 1,500 / 0.06 = 25 MVA. hr = √(25,000 / 500) = 7.07, right on the 7th.", "ref": "" }, { "id": "MV512-028", "module": "MV-512", "level": "P", "region": "All", "question": "Why does the parallel resonance move as capacitor steps switch in?", "options": [ "hr depends on Qc, so adding kvar lowers the resonant order, often passing through the 5th and 7th", "It does not move", "The voltage changes", "The transformer changes" ], "answer": 0, "explanation": "Plain banks can resonate at some step positions even if the full bank does not.", "ref": "" }, { "id": "MV512-029", "module": "MV-512", "level": "P", "region": "All", "question": "In which sequence does the 5th harmonic rotate in a balanced three-phase system?", "options": [ "It does not rotate", "Zero", "Positive", "Negative" ], "answer": 3, "explanation": "5th is negative, 7th positive and 3rd zero sequence. Negative sequence harmonics produce braking torque in motors.", "ref": "" }, { "id": "MV512-030", "module": "MV-512", "level": "P", "region": "All", "question": "A load draws I1 = 100 A with current THD of 30%. What is the total rms current?", "options": [ "109 A", "100 A", "130 A", "104 A" ], "answer": 3, "explanation": "Irms = 100 x √(1 + 0.3²) = 104.4 A.", "ref": "" }, { "id": "MV512-031", "module": "MV-512", "level": "P", "region": "All", "question": "A drive has displacement power factor 0.95 and current THD of 40%. What is the approximate true power factor?", "options": [ "0.57", "0.76", "0.88", "0.95" ], "answer": 2, "explanation": "True PF ≈ DPF / √(1 + THD²) = 0.95 / √1.16 = 0.88.", "ref": "" }, { "id": "MV512-032", "module": "MV-512", "level": "P", "region": "All", "question": "Phase voltages read 400 V, 408 V and 392 V. Using the NEMA method, what is the voltage unbalance?", "options": [ "8%", "2%", "4%", "1%" ], "answer": 1, "explanation": "Average is 400 V. Maximum deviation is 8 V. 8 / 400 = 2%.", "ref": "" }, { "id": "MV512-033", "module": "MV-512", "level": "P", "region": "All", "question": "Each phase of a three-phase IT load carries 30 A of 3rd harmonic. Roughly how much 3rd harmonic current flows in the neutral?", "options": [ "52 A", "0 A", "90 A", "30 A" ], "answer": 2, "explanation": "Triplen currents add arithmetically in the neutral: 3 x 30 = 90 A at 150 Hz.", "ref": "" }, { "id": "MV512-034", "module": "MV-512", "level": "P", "region": "All", "question": "Which IEC standard defines class A power quality measurement methods?", "options": [ "IEC 61000-4-30", "IEC 60076-1", "IEC 60909", "IEC 61439" ], "answer": 0, "explanation": "Class A instruments give comparable results between meters for compliance work.", "ref": "IEC 61000-4-30" }, { "id": "MV512-035", "module": "MV-512", "level": "P", "region": "AU", "question": "Which standard do Australian and New Zealand network operators use for allocating harmonic emission limits to MV customers?", "options": [ "AS 2067", "AS/NZS 3008", "AS/NZS 61000.3.6", "AS/NZS 3000" ], "answer": 2, "explanation": "It adopts IEC 61000-3-6 with local variations.", "ref": "AS/NZS 61000.3.6" }, { "id": "MV512-036", "module": "MV-512", "level": "P", "region": "KSA", "question": "What frequency does a 7% detuned reactor tune a bank to on a 60 Hz system such as in Saudi Arabia?", "options": [ "210 Hz", "227 Hz", "189 Hz", "300 Hz" ], "answer": 1, "explanation": "60 / √0.07 = 227 Hz, still below the 5th harmonic at 300 Hz.", "ref": "" }, { "id": "MV512-037", "module": "MV-512", "level": "E", "region": "All", "question": "For a load with I1 = 1.0 pu and I5 = 0.3 pu only, what is the K-factor (based on total rms current)?", "options": [ "3.0", "7.5", "2.0", "1.0" ], "answer": 0, "explanation": "K = Σ(Ih² h²) / Σ Ih² = (1 + 0.09 x 25) / 1.09 = 2.98.", "ref": "" }, { "id": "MV512-038", "module": "MV-512", "level": "E", "region": "All", "question": "A series reactor of p = 7% raises the voltage across the capacitors on a 400 V system to about...", "options": [ "372 V", "400 V", "525 V", "430 V" ], "answer": 3, "explanation": "Uc = U / (1 - p) = 400 / 0.93 = 430 V, so capacitors rated 440 V or more are used.", "ref": "" }, { "id": "MV512-039", "module": "MV-512", "level": "E", "region": "All", "question": "A capacitor rated 100 kvar at 440 V is run at 400 V. What kvar does it give?", "options": [ "About 100 kvar", "About 110 kvar", "About 83 kvar", "About 91 kvar" ], "answer": 2, "explanation": "Output scales with V²: 100 x (400/440)² = 82.6 kvar.", "ref": "IEC 60831-1" }, { "id": "MV512-040", "module": "MV-512", "level": "E", "region": "All", "question": "A passive filter for the 5th harmonic is usually tuned to about the 4.7th rather than exactly the 5th. Why?", "options": [ "It is a typing error", "To filter the 3rd", "To save cost", "So tolerance drift and capacitor ageing do not move it above the 5th, and it avoids sinking all upstream 5th harmonics" ], "answer": 3, "explanation": "Capacitance falls with ageing, which raises the tuned frequency, so designers tune slightly low.", "ref": "" }, { "id": "MV512-041", "module": "MV-512", "level": "E", "region": "All", "question": "Why is a 14% reactor chosen instead of 7% in some installations?", "options": [ "Where significant 3rd harmonics exist, since 7% tuning at 189 Hz sits too close to 150 Hz", "For 60 Hz only", "To increase kvar output", "It is cheaper" ], "answer": 0, "explanation": "14% tunes to 134 Hz, below the 3rd harmonic at 150 Hz.", "ref": "" }, { "id": "MV512-042", "module": "MV-512", "level": "E", "region": "All", "question": "A 2,000 kVA, 6% transformer feeds a 300 kvar plain bank. Ignoring the source impedance, near which order is the resonance?", "options": [ "About 10.5", "About 7.1", "About 5.0", "About 15.0" ], "answer": 0, "explanation": "Ssc ≈ 2,000 / 0.06 = 33.3 MVA. √(33,333 / 300) = 10.5, between the 7th and 11th.", "ref": "" }, { "id": "MV512-043", "module": "MV-512", "level": "E", "region": "All", "question": "Twelve 10 minute Pst values are six of 0.8 and six of 1.2. What is Plt?", "options": [ "1.20", "1.00", "1.04", "0.80" ], "answer": 2, "explanation": "Plt = cube root of the mean of Pst³ = ∛((6 x 0.512 + 6 x 1.728) / 12) = 1.04.", "ref": "IEC 61000-4-15" }, { "id": "MV512-044", "module": "MV-512", "level": "E", "region": "All", "question": "How is voltage unbalance defined in IEC 61000 standards?", "options": [ "Negative sequence voltage divided by positive sequence voltage", "Average voltage divided by nominal", "Zero sequence current divided by phase current", "Highest phase voltage divided by lowest" ], "answer": 0, "explanation": "The NEMA maximum deviation method is a close approximation for small unbalance.", "ref": "IEC 61000-4-30" }, { "id": "MV512-045", "module": "MV-512", "level": "E", "region": "All", "question": "Which harmonics does a 12-pulse rectifier mainly produce?", "options": [ "2nd and 4th", "5th and 7th", "3rd and 9th", "11th and 13th" ], "answer": 3, "explanation": "Characteristic harmonics are h = 12k ± 1, so the 5th and 7th largely cancel.", "ref": "" }, { "id": "MV512-046", "module": "MV-512", "level": "E", "region": "All", "question": "Why can a voltage THD measurement at light load look acceptable when IEEE 519 compliance is still at risk?", "options": [ "Harmonic currents and voltage distortion grow at full load, and background distortion from the network varies with time", "IEEE 519 ignores load", "Light load raises THD", "THD never changes" ], "answer": 0, "explanation": "IEEE 519 assesses statistics over a week, such as 95th and 99th percentile values.", "ref": "IEEE 519" }, { "id": "MV512-047", "module": "MV-512", "level": "E", "region": "All", "question": "Why do harmonics increase transformer eddy current losses more than their current magnitude suggests?", "options": [ "Only iron losses change", "Harmonics reduce losses", "They do not", "Winding eddy losses rise with the square of harmonic order as well as the square of current" ], "answer": 3, "explanation": "This h² weighting is what the K-factor and IEEE C57.110 derating capture.", "ref": "IEEE C57.110" }, { "id": "MV512-048", "module": "MV-512", "level": "E", "region": "GCC", "question": "A GCC tower has many chiller VFDs and a plain capacitor bank that keeps failing. What is the most likely fix?", "options": [ "Raise the voltage", "Replace it with a detuned bank or add an active filter, after a harmonic survey", "Remove all VFDs", "Bigger fuses" ], "answer": 1, "explanation": "A plain bank resonating near the 5th or 7th is a classic cause of capacitor failures.", "ref": "" }, { "id": "MV512-049", "module": "MV-512", "level": "P", "region": "Asia", "question": "In Malaysia, which utility publishes power factor and harmonic requirements in its supply guidelines?", "options": [ "TNB", "SP Group", "CLP", "PLN" ], "answer": 0, "explanation": "Tenaga Nasional Berhad sets these, often based on IEC 61000 and IEEE 519.", "ref": "" }, { "id": "MV512-050", "module": "MV-512", "level": "B", "region": "NZ", "question": "What do New Zealand lines companies usually set in their connection rules for reactive power?", "options": [ "A minimum power factor at the point of supply", "A fixed harmonic order", "A maximum kW only", "A maximum cable length" ], "answer": 0, "explanation": "Customers below the required power factor may need correction or face charges.", "ref": "" }, { "id": "MV513-001", "module": "MV-513", "level": "B", "region": "All", "question": "When does a fixed-tilt solar PV system usually produce its peak output?", "options": [ "Around midnight", "Just before sunrise", "Early evening", "Around midday" ], "answer": 3, "explanation": "PV output follows the sun, so it peaks near solar noon on a clear day.", "ref": "" }, { "id": "MV513-002", "module": "MV-513", "level": "B", "region": "All", "question": "What is reverse power flow at an MV connection?", "options": [ "Negative sequence current", "Power flowing from the site back into the network", "Load being shed by the utility", "Current flowing in the earth conductor" ], "answer": 1, "explanation": "It happens when on-site generation is greater than the site load at that moment.", "ref": "" }, { "id": "MV513-003", "module": "MV-513", "level": "B", "region": "All", "question": "What does BESS stand for?", "options": [ "Base Electrical Supply Station", "Backup Emergency Switching System", "Busbar Earthing Safety System", "Battery Energy Storage System" ], "answer": 3, "explanation": "A BESS stores energy in batteries and delivers it through an inverter.", "ref": "" }, { "id": "MV513-004", "module": "MV-513", "level": "B", "region": "All", "question": "In peak shaving, what does the battery do?", "options": [ "Corrects the frequency only", "Disconnects the building", "Discharges during the peak so the grid sees a lower demand", "Charges during the peak to raise demand" ], "answer": 2, "explanation": "The battery supplies the part of the load above the peak target.", "ref": "" }, { "id": "MV513-005", "module": "MV-513", "level": "B", "region": "All", "question": "A battery rated 1 MW / 2 MWh tells you what?", "options": [ "It can deliver up to 1 MW and store 2 MWh, so about 2 hours at full power", "It needs 2 MW to charge", "It stores 1 MWh", "It can deliver 2 MW for 1 hour" ], "answer": 0, "explanation": "kW or MW is the power rating, kWh or MWh is the energy it can store.", "ref": "" }, { "id": "MV513-006", "module": "MV-513", "level": "B", "region": "All", "question": "What does SoC mean for a battery?", "options": [ "Source of Current", "System Operating Code", "Speed of Charging", "State of Charge, the stored energy as a percentage of capacity" ], "answer": 3, "explanation": "SoC shows how full the battery is, from 0 to 100%.", "ref": "" }, { "id": "MV513-007", "module": "MV-513", "level": "B", "region": "All", "question": "What is anti-islanding protection on a grid-connected inverter for?", "options": [ "To limit harmonics", "To stop the inverter energising a network that the utility has disconnected", "To raise output on cloudy days", "To charge the battery at night" ], "answer": 1, "explanation": "It protects line workers and equipment when the grid is lost.", "ref": "" }, { "id": "MV513-008", "module": "MV-513", "level": "B", "region": "All", "question": "Exporting active power through a feeder usually does what to the local voltage?", "options": [ "Has no effect", "Raises it", "Lowers it", "Changes the frequency instead" ], "answer": 1, "explanation": "Current flowing out through the feeder resistance raises the voltage at the connection point.", "ref": "" }, { "id": "MV513-009", "module": "MV-513", "level": "B", "region": "All", "question": "Which inverter action helps offset voltage rise from export?", "options": [ "Injecting more active power", "Raising the frequency", "Absorbing reactive power", "Switching off the meter" ], "answer": 2, "explanation": "Absorbing Q gives a negative Q x X term that cancels part of the P x R rise.", "ref": "" }, { "id": "MV513-010", "module": "MV-513", "level": "B", "region": "All", "question": "What typical power range do DC fast chargers for cars cover?", "options": [ "3 to 7 kW", "11 to 22 kW", "1 to 5 MW", "About 50 to 350 kW" ], "answer": 3, "explanation": "DC fast chargers are commonly 50 kW, with high power units up to about 350 kW.", "ref": "" }, { "id": "MV513-011", "module": "MV-513", "level": "B", "region": "All", "question": "Why is diversity applied when sizing a supply for many EV chargers?", "options": [ "Chargers never run", "It increases the transformer size", "It is a utility fee", "Not all chargers draw full power at the same time" ], "answer": 3, "explanation": "Cars arrive at different times and taper their charging as the battery fills.", "ref": "" }, { "id": "MV513-012", "module": "MV-513", "level": "B", "region": "AU", "question": "Which standard covers grid connection of inverter energy systems in Australia and New Zealand?", "options": [ "IEC 60909", "AS/NZS 3008", "IEEE 80", "AS/NZS 4777" ], "answer": 3, "explanation": "AS/NZS 4777.1 covers installation and 4777.2 covers inverter requirements.", "ref": "AS/NZS 4777" }, { "id": "MV513-013", "module": "MV-513", "level": "B", "region": "GCC", "question": "What is the name of the DEWA programme for rooftop solar connected to the Dubai grid?", "options": [ "Green Dubai Grid", "Noor Dubai", "Shams Dubai", "Sun Link" ], "answer": 2, "explanation": "Shams Dubai lets building owners connect PV under DEWA distributed renewable rules.", "ref": "DEWA DRRG" }, { "id": "MV513-014", "module": "MV-513", "level": "B", "region": "All", "question": "Which IEC standard covers conductive EV charging systems?", "options": [ "IEC 61851", "IEC 60076", "IEC 60599", "IEC 62271" ], "answer": 0, "explanation": "IEC 61851 covers the general requirements and charging modes.", "ref": "IEC 61851" }, { "id": "MV513-015", "module": "MV-513", "level": "B", "region": "All", "question": "What is an export limit at a connection?", "options": [ "The maximum import current", "A cap on how much power the site may send back to the network", "A battery fire rating", "The PV panel rating" ], "answer": 1, "explanation": "Utilities set export limits where the network cannot absorb more generation.", "ref": "" }, { "id": "MV513-016", "module": "MV-513", "level": "B", "region": "All", "question": "Roughly how much fault current does an inverter contribute?", "options": [ "The same as a synchronous generator", "Zero", "10 to 20 times rated current", "About 1.1 to 1.5 times rated current" ], "answer": 3, "explanation": "Inverters electronically limit their current, which affects protection grading.", "ref": "" }, { "id": "MV513-017", "module": "MV-513", "level": "B", "region": "All", "question": "Why do residential EV hubs often push the site peak later in the day?", "options": [ "Solar is highest then", "Chargers only work at night", "Cars plug in when people get home in the evening", "Tariffs force it" ], "answer": 2, "explanation": "Evening arrival adds load on top of the building evening peak.", "ref": "" }, { "id": "MV513-018", "module": "MV-513", "level": "B", "region": "NZ", "question": "In New Zealand, which part of the Electricity Industry Participation Code covers connection of distributed generation?", "options": [ "Part 12", "Part 6", "Part 15", "Part 1" ], "answer": 1, "explanation": "Part 6 sets the application process for connecting distributed generation to a distribution network.", "ref": "" }, { "id": "MV513-019", "module": "MV-513", "level": "B", "region": "All", "question": "A smart charging system for EVs mainly does what?", "options": [ "Adjusts charging power to stay within the site capacity", "Measures tyre pressure", "Raises charger power above rating", "Replaces the transformer" ], "answer": 0, "explanation": "Load management shares the available capacity among the cars.", "ref": "" }, { "id": "MV513-020", "module": "MV-513", "level": "P", "region": "All", "question": "Using dV% = (PR + QX)/V² x 100, what is the rise for 1.5 MW export at unity power factor on 11 kV through R = 1.2 ohm?", "options": [ "About 15%", "About 0.15%", "About 5%", "About 1.5%" ], "answer": 3, "explanation": "1.5 x 1.2 / 11² x 100 = 1.49%. Units are MW, ohm and kV.", "ref": "" }, { "id": "MV513-021", "module": "MV-513", "level": "P", "region": "All", "question": "The same 1.5 MW export on 11 kV (R = 1.2, X = 1.0 ohm) runs at 0.95 power factor absorbing. About what is the rise now?", "options": [ "0.4%", "1.5%", "1.9%", "1.1%" ], "answer": 3, "explanation": "Q = 1.5 x tan(acos 0.95) = 0.49 Mvar absorbed. (1.8 - 0.49) / 121 x 100 = 1.08%.", "ref": "" }, { "id": "MV513-022", "module": "MV-513", "level": "P", "region": "All", "question": "What is the voltage rise for 2 MW at unity power factor on 22 kV through R = 2 ohm?", "options": [ "About 0.4%", "About 0.8%", "About 1.6%", "About 8%" ], "answer": 1, "explanation": "2 x 2 / 22² x 100 = 0.83%.", "ref": "" }, { "id": "MV513-023", "module": "MV-513", "level": "P", "region": "All", "question": "A 500 kW battery must cover a peak for 2 hours. What is the minimum usable energy?", "options": [ "2,000 kWh", "500 kWh", "250 kWh", "1,000 kWh" ], "answer": 3, "explanation": "500 kW x 2 h = 1,000 kWh, before allowing for depth of discharge and ageing.", "ref": "" }, { "id": "MV513-024", "module": "MV-513", "level": "P", "region": "All", "question": "What is the C-rate of a 1 MW / 4 MWh battery at full power?", "options": [ "0.25C", "4C", "1C", "0.5C" ], "answer": 0, "explanation": "C-rate = power / energy = 1 / 4 = 0.25C, a 4 hour battery.", "ref": "" }, { "id": "MV513-025", "module": "MV-513", "level": "P", "region": "All", "question": "A 2 MWh battery is limited to 90% depth of discharge. What usable energy does it give?", "options": [ "0.9 MWh", "1.8 MWh", "2.0 MWh", "2.2 MWh" ], "answer": 1, "explanation": "2 x 0.9 = 1.8 MWh.", "ref": "" }, { "id": "MV513-026", "module": "MV-513", "level": "P", "region": "All", "question": "A building runs 0.4 MW above the peak target for 3 hours. What battery is needed at minimum?", "options": [ "1.2 MW / 0.4 MWh", "3 MW / 1.2 MWh", "0.4 MW / 1.2 MWh", "0.4 MW / 0.4 MWh" ], "answer": 2, "explanation": "Power is the excess above target (0.4 MW). Energy is 0.4 x 3 = 1.2 MWh, plus margins.", "ref": "" }, { "id": "MV513-027", "module": "MV-513", "level": "P", "region": "All", "question": "With 90% round-trip efficiency, how much energy must go in to get 0.9 MWh out?", "options": [ "1.0 MWh", "1.8 MWh", "0.81 MWh", "0.9 MWh" ], "answer": 0, "explanation": "0.9 / 0.9 = 1.0 MWh charged.", "ref": "" }, { "id": "MV513-028", "module": "MV-513", "level": "P", "region": "All", "question": "A car park has ten 150 kW DC chargers and a diversity factor of 0.6. What design demand results?", "options": [ "600 kW", "1,500 kW", "150 kW", "900 kW" ], "answer": 3, "explanation": "10 x 150 x 0.6 = 900 kW.", "ref": "" }, { "id": "MV513-029", "module": "MV-513", "level": "P", "region": "All", "question": "A 1 MWp PV array sees 5.5 peak sun hours with a performance ratio of 0.8. About what is the daily yield?", "options": [ "5.5 MWh", "0.8 MWh", "6.9 MWh", "4.4 MWh" ], "answer": 3, "explanation": "1 x 5.5 x 0.8 = 4.4 MWh.", "ref": "" }, { "id": "MV513-030", "module": "MV-513", "level": "P", "region": "All", "question": "At midday PV gives 2.0 MW, the load is 0.8 MW and the export limit is 0.5 MW. How much must be absorbed by a battery or curtailed?", "options": [ "1.2 MW", "0.5 MW", "0.7 MW", "2.0 MW" ], "answer": 2, "explanation": "Surplus = 2.0 - 0.8 = 1.2 MW. Only 0.5 MW may be exported, so 0.7 MW must be stored or curtailed.", "ref": "" }, { "id": "MV513-031", "module": "MV-513", "level": "P", "region": "All", "question": "What does volt-var mode do on a smart inverter?", "options": [ "Changes reactive power with the local voltage", "Limits DC current only", "Switches off at night", "Changes frequency with voltage" ], "answer": 0, "explanation": "It absorbs vars when voltage is high and can supply vars when voltage is low.", "ref": "AS/NZS 4777.2" }, { "id": "MV513-032", "module": "MV-513", "level": "P", "region": "All", "question": "What does volt-watt mode do?", "options": [ "Measures the energy exported", "Raises active power when voltage is high", "Controls the battery temperature", "Reduces active power output as the voltage rises above a set point" ], "answer": 3, "explanation": "Curtailing P limits the P x R component of voltage rise.", "ref": "AS/NZS 4777.2" }, { "id": "MV513-033", "module": "MV-513", "level": "P", "region": "All", "question": "Why must protection be reviewed when large PV is added behind a building transformer?", "options": [ "Power can flow backwards and inverter fault current is low, which can affect directional and overcurrent settings", "Inverters double the fault level", "Fuses get bigger automatically", "The CTs stop working" ], "answer": 0, "explanation": "Reverse flow and limited fault current change how relays see faults.", "ref": "" }, { "id": "MV513-034", "module": "MV-513", "level": "P", "region": "AU", "question": "Why do many Australian distributors use dynamic export limits?", "options": [ "To replace AS/NZS 4777", "To raise the frequency", "To allow more export when the local network has capacity and less when it does not", "To charge for metering" ], "answer": 2, "explanation": "High rooftop PV uptake means fixed limits are often too strict or too loose at different times.", "ref": "" }, { "id": "MV513-035", "module": "MV-513", "level": "P", "region": "AU", "question": "For large generating plant in the National Electricity Market, which set of requirements applies?", "options": [ "IEC 60364 only", "AEMO generator performance standards under the National Electricity Rules", "The building code only", "AS/NZS 3008" ], "answer": 1, "explanation": "Large plant must meet negotiated generator performance standards, while small inverters follow AS/NZS 4777.", "ref": "" }, { "id": "MV513-036", "module": "MV-513", "level": "P", "region": "GCC", "question": "Under Shams Dubai, what must the inverter normally be?", "options": [ "Any inverter with a CE mark", "Locally manufactured", "Rated above 1 MW", "An inverter on the DEWA approved equipment list" ], "answer": 3, "explanation": "DEWA publishes eligible equipment lists for distributed renewable connections.", "ref": "DEWA DRRG" }, { "id": "MV513-037", "module": "MV-513", "level": "P", "region": "All", "question": "A 1,000 kVA transformer at 0.95 power factor supplies a site whose load plus EV charging reaches 1,100 kW for 2 hours. What is the most direct non-wiring fix?", "options": [ "Reduce the PV size", "Add a capacitor bank only", "Change the vector group", "Add a battery or smart charging to cover about 150 kW for 2 hours" ], "answer": 3, "explanation": "1,000 kVA x 0.95 = 950 kW. The 150 kW excess for 2 hours needs about 300 kWh from a battery or managed charging.", "ref": "" }, { "id": "MV513-038", "module": "MV-513", "level": "P", "region": "All", "question": "Why does an EV hub need a power quality check?", "options": [ "They make the load capacitive at all times", "Chargers draw only DC from the grid", "They lower the voltage to zero", "Chargers are power electronic loads that can inject harmonics" ], "answer": 3, "explanation": "Rectifier front ends produce harmonic currents that must meet the utility limits.", "ref": "" }, { "id": "MV513-039", "module": "MV-513", "level": "E", "region": "All", "question": "On a cable feeder with a low X/R ratio, why does reactive power absorption help less with voltage rise?", "options": [ "Cables have no resistance", "X is small, so the Q x X term is small compared with P x R", "Inverters cannot absorb vars on cables", "Reactive power cannot flow in cables" ], "answer": 1, "explanation": "Where R dominates, active power curtailment (volt-watt) is often needed.", "ref": "" }, { "id": "MV513-040", "module": "MV-513", "level": "E", "region": "All", "question": "A 3 MW export on 33 kV through R = 0.5 ohm, unity power factor, gives about what rise?", "options": [ "0.45%", "0.14%", "4.5%", "1.4%" ], "answer": 1, "explanation": "3 x 0.5 / 33² x 100 = 0.14%. Higher voltage connections see much smaller rise for the same power.", "ref": "" }, { "id": "MV513-041", "module": "MV-513", "level": "E", "region": "All", "question": "Why can a voltage-rise problem appear at light load on a sunny weekend rather than on a weekday?", "options": [ "PV output falls at weekends", "Load is lowest, so most PV output is exported", "The tap changer raises its set point", "Transformers are switched off" ], "answer": 1, "explanation": "Minimum load with maximum generation gives the largest export and highest voltage.", "ref": "" }, { "id": "MV513-042", "module": "MV-513", "level": "E", "region": "All", "question": "Which anti-islanding approach uses active methods inside the inverter?", "options": [ "Waiting for a fuse to blow", "Measuring cable temperature", "Using a larger transformer", "Small deliberate frequency or reactive power perturbations to detect loss of grid" ], "answer": 3, "explanation": "Active methods push the island out of the trip window, reducing the non-detection zone.", "ref": "IEEE 1547" }, { "id": "MV513-043", "module": "MV-513", "level": "E", "region": "All", "question": "Why is a BESS energy rating usually oversized above the calculated peak-shave energy?", "options": [ "To allow for depth of discharge limits, round-trip losses and capacity fade over life", "To increase the C-rate", "To make the inverter smaller", "Utilities require double size" ], "answer": 0, "explanation": "End of life usable capacity must still cover the peak.", "ref": "" }, { "id": "MV513-044", "module": "MV-513", "level": "E", "region": "All", "question": "A transformer that sees reverse power from PV may need what change?", "options": [ "Removal of the neutral earth", "A check of the tap position and voltage regulation, since export raises the LV voltage", "A different vector group in all cases", "A larger LV cable only" ], "answer": 1, "explanation": "Off-load taps set for import can leave the LV high during export.", "ref": "" }, { "id": "MV513-045", "module": "MV-513", "level": "E", "region": "All", "question": "For a BESS that also gives backup during an outage, what must the system be able to do that a grid-following inverter cannot?", "options": [ "Form its own voltage and frequency reference (grid-forming) in a planned island", "Charge from PV", "Export to the grid", "Measure SoC" ], "answer": 0, "explanation": "Grid-following inverters need an external reference, so backup needs a grid-forming mode and intentional islanding controls.", "ref": "" }, { "id": "MV513-046", "module": "MV-513", "level": "E", "region": "All", "question": "Why can large single-phase EV charging on an LV network be a problem?", "options": [ "It removes harmonics", "It lowers the fault level", "It raises the frequency", "It causes voltage unbalance between phases" ], "answer": 3, "explanation": "Uneven phase loading raises neutral current and unbalance.", "ref": "" }, { "id": "MV513-047", "module": "MV-513", "level": "E", "region": "Asia", "question": "Which scheme in Malaysia lets consumers offset their bill with rooftop solar export?", "options": [ "Smart Export Guarantee", "Net Energy Metering (NEM)", "Shams Dubai", "Feed-in Premium Rule" ], "answer": 1, "explanation": "Malaysia runs a net energy metering programme for rooftop PV.", "ref": "" }, { "id": "MV513-048", "module": "MV-513", "level": "E", "region": "KSA", "question": "In Saudi Arabia, small-scale rooftop PV connected to the distribution network is regulated by whom?", "options": [ "AEMO", "The national electricity regulator and the national utility rules", "Transpower", "DEWA" ], "answer": 1, "explanation": "The Saudi regulator and the utility set the small-scale PV connection rules, which change over time, so check the current versions.", "ref": "" }, { "id": "MV514-001", "module": "MV-514", "level": "B", "region": "All", "question": "What does a merging unit do in a digital substation?", "options": [ "Controls the HMI screens", "Digitises CT and VT signals and publishes them as sampled values", "Merges two busbars", "Stores alarm history" ], "answer": 1, "explanation": "It replaces copper analogue wiring with sampled values on the process bus.", "ref": "IEC 61850-9-2" }, { "id": "MV514-002", "module": "MV-514", "level": "B", "region": "All", "question": "What is a GOOSE message used for?", "options": [ "Billing data", "Fast trips, interlocks and status between IEDs", "Long-term archiving", "Video surveillance" ], "answer": 1, "explanation": "GOOSE is a fast Layer 2 multicast message.", "ref": "IEC 61850-8-1" }, { "id": "MV514-003", "module": "MV-514", "level": "B", "region": "All", "question": "Which bus connects merging units and switchgear controllers to protection IEDs?", "options": [ "Station bus", "Control centre WAN", "Field bus RS-485", "Process bus" ], "answer": 3, "explanation": "The process bus carries sampled values and GOOSE at bay level.", "ref": "" }, { "id": "MV514-004", "module": "MV-514", "level": "B", "region": "All", "question": "Which bus connects IEDs to the HMI and the gateway?", "options": [ "Process bus", "Station bus", "DC bus", "Analogue bus" ], "answer": 1, "explanation": "The station bus carries MMS reports, controls and interlocking GOOSE.", "ref": "" }, { "id": "MV514-005", "module": "MV-514", "level": "B", "region": "All", "question": "What does the logical node XCBR represent?", "options": [ "A circuit breaker", "A current transformer", "A measurement unit", "A distance relay" ], "answer": 0, "explanation": "X is the switchgear group and CBR means circuit breaker.", "ref": "IEC 61850-7-4" }, { "id": "MV514-006", "module": "MV-514", "level": "B", "region": "All", "question": "Which logical node is time overcurrent protection?", "options": [ "PTOC", "XSWI", "PDIS", "MMXU" ], "answer": 0, "explanation": "PTOC is time overcurrent, PIOC is instantaneous overcurrent.", "ref": "IEC 61850-7-4" }, { "id": "MV514-007", "module": "MV-514", "level": "B", "region": "All", "question": "Which logical node is distance protection?", "options": [ "PDIF", "PTOV", "PDIS", "RREC" ], "answer": 2, "explanation": "PDIS is distance, PDIF is differential.", "ref": "IEC 61850-7-4" }, { "id": "MV514-008", "module": "MV-514", "level": "B", "region": "All", "question": "Which logical node provides measured values such as current, voltage and power?", "options": [ "TCTR", "XCBR", "MMXU", "CSWI" ], "answer": 2, "explanation": "MMXU gives measurement values for operational use.", "ref": "IEC 61850-7-4" }, { "id": "MV514-009", "module": "MV-514", "level": "B", "region": "All", "question": "How many samples per cycle does protection-class sampled values use under 9-2LE?", "options": [ "16", "1,000", "256", "80" ], "answer": 3, "explanation": "80 samples per cycle for protection, 256 for metering and power quality.", "ref": "IEC 61850-9-2 LE" }, { "id": "MV514-010", "module": "MV-514", "level": "B", "region": "All", "question": "What does PRP stand for?", "options": [ "Primary Relay Protection", "Process Ring Path", "Protected Route Protocol", "Parallel Redundancy Protocol" ], "answer": 3, "explanation": "PRP sends each frame over two independent LANs.", "ref": "IEC 62439-3" }, { "id": "MV514-011", "module": "MV-514", "level": "B", "region": "All", "question": "How long does PRP take to recover from a single link failure?", "options": [ "About 30 seconds", "About 2 seconds", "Zero, because the duplicate frame still arrives", "About 50 ms" ], "answer": 2, "explanation": "Nothing needs to reconfigure, so no data is lost.", "ref": "IEC 62439-3" }, { "id": "MV514-012", "module": "MV-514", "level": "B", "region": "All", "question": "What does HSR do with each frame?", "options": [ "Sends it once round a ring", "Sends it over wireless", "Sends it both ways round a ring", "Stores it until acknowledged" ], "answer": 2, "explanation": "The receiver takes the first copy and discards the duplicate.", "ref": "IEC 62439-3" }, { "id": "MV514-013", "module": "MV-514", "level": "B", "region": "All", "question": "Which protocol is used for precise time synchronisation on the process bus?", "options": [ "SNMP", "IEEE 1588 PTP", "NTP", "IRIG-A over copper only" ], "answer": 1, "explanation": "PTP gives about 1 microsecond accuracy, defined for power utilities in IEC 61850-9-3.", "ref": "IEC 61850-9-3" }, { "id": "MV514-014", "module": "MV-514", "level": "B", "region": "All", "question": "What does SCL stand for in IEC 61850?", "options": [ "Substation Configuration Language", "Station Control Logic", "Sampled Current Level", "Serial Communication Link" ], "answer": 0, "explanation": "SCL is an XML language describing IEDs, data and communication.", "ref": "IEC 61850-6" }, { "id": "MV514-015", "module": "MV-514", "level": "B", "region": "All", "question": "Which two protocols commonly link a substation gateway to the control centre?", "options": [ "HTTP and FTP", "Bluetooth and Zigbee", "IEC 60870-5-104 and DNP3", "Modbus RTU and CANbus" ], "answer": 2, "explanation": "Both are standard telecontrol protocols over IP.", "ref": "" }, { "id": "MV514-016", "module": "MV-514", "level": "B", "region": "All", "question": "Which IEC series covers cyber security for power system communication protocols?", "options": [ "IEC 61439", "IEC 60287", "IEC 62351", "IEC 60599" ], "answer": 2, "explanation": "IEC 62351 adds security to protocols such as MMS, GOOSE, SV and IEC 104.", "ref": "IEC 62351" }, { "id": "MV514-017", "module": "MV-514", "level": "B", "region": "All", "question": "Which protocol carries client-server reports and controls between IEDs and the HMI in IEC 61850?", "options": [ "PTP", "GOOSE", "MMS", "Sampled values" ], "answer": 2, "explanation": "MMS runs over TCP/IP on the station bus.", "ref": "IEC 61850-8-1" }, { "id": "MV514-018", "module": "MV-514", "level": "B", "region": "All", "question": "What is the main benefit of replacing copper with a process bus?", "options": [ "Much less copper wiring and easier testing and reconfiguration", "Higher fault level", "No need for time sync", "No need for protection" ], "answer": 0, "explanation": "Signals become data on fibre, which cuts wiring and CT open-circuit hazards.", "ref": "" }, { "id": "MV514-019", "module": "MV-514", "level": "B", "region": "AU", "question": "Which telecontrol protocol is widely used for distribution SCADA in Australia and New Zealand?", "options": [ "PROFIBUS", "KNX", "BACnet", "DNP3" ], "answer": 3, "explanation": "DNP3 (IEEE 1815) is common for RTUs and field devices in AU and NZ.", "ref": "IEEE 1815" }, { "id": "MV514-020", "module": "MV-514", "level": "P", "region": "All", "question": "How many SV frames per second are sent at 80 samples per cycle on a 50 Hz system?", "options": [ "50,000", "800", "4,000", "80" ], "answer": 2, "explanation": "80 x 50 = 4,000 frames per second.", "ref": "" }, { "id": "MV514-021", "module": "MV-514", "level": "P", "region": "KSA", "question": "How many SV frames per second are sent at 80 samples per cycle on a 60 Hz system such as Saudi Arabia?", "options": [ "4,800", "4,000", "6,000", "8,000" ], "answer": 0, "explanation": "80 x 60 = 4,800 frames per second.", "ref": "" }, { "id": "MV514-022", "module": "MV-514", "level": "P", "region": "All", "question": "One SV stream sends 4,000 frames per second of 160 bytes each. What is the bandwidth?", "options": [ "640 Mbit/s", "5.12 Mbit/s", "51.2 Mbit/s", "0.64 Mbit/s" ], "answer": 1, "explanation": "4,000 x 160 x 8 = 5.12 Mbit/s.", "ref": "" }, { "id": "MV514-023", "module": "MV-514", "level": "P", "region": "All", "question": "Eight merging units each send 5.12 Mbit/s. About what share of a 100 Mbit/s link do they use?", "options": [ "41%", "100%", "82%", "4%" ], "answer": 0, "explanation": "8 x 5.12 = 40.96 Mbit/s, about 41% before GOOSE and other traffic.", "ref": "" }, { "id": "MV514-024", "module": "MV-514", "level": "P", "region": "All", "question": "What is the IEC 61850-5 transfer time target for fast trip GOOSE messages?", "options": [ "3 ms", "100 ms", "30 ms", "1 s" ], "answer": 0, "explanation": "Trips are in the fastest transfer time class, TT6, at 3 ms.", "ref": "IEC 61850-5" }, { "id": "MV514-025", "module": "MV-514", "level": "P", "region": "All", "question": "After a state change, how is a GOOSE message repeated?", "options": [ "Never repeated", "Only when asked by the HMI", "Fast at first, then at growing intervals up to a heartbeat time", "Once per hour" ], "answer": 2, "explanation": "Repetition makes sure the message gets through without acknowledgements.", "ref": "IEC 61850-8-1" }, { "id": "MV514-026", "module": "MV-514", "level": "P", "region": "All", "question": "In a GOOSE message, what does stNum count?", "options": [ "Network hops", "State changes of the dataset", "Retransmissions of the same state", "IED serial number" ], "answer": 1, "explanation": "stNum increases on each change, sqNum increases on each repeat of the same state.", "ref": "IEC 61850-8-1" }, { "id": "MV514-027", "module": "MV-514", "level": "P", "region": "All", "question": "Which SCL file describes the capability of a single IED as supplied by the vendor?", "options": [ "ICD", "SCD", "SSD", "CID" ], "answer": 0, "explanation": "ICD is the IED Capability Description.", "ref": "IEC 61850-6" }, { "id": "MV514-028", "module": "MV-514", "level": "P", "region": "All", "question": "Which SCL file describes the whole configured substation, including all IEDs and data flows?", "options": [ "ICD", "IID", "CID", "SCD" ], "answer": 3, "explanation": "SCD is the Substation Configuration Description.", "ref": "IEC 61850-6" }, { "id": "MV514-029", "module": "MV-514", "level": "P", "region": "All", "question": "Which SCL file is loaded into one IED as its final configuration?", "options": [ "CID", "SCD", "ICD", "SSD" ], "answer": 0, "explanation": "CID is the Configured IED Description.", "ref": "IEC 61850-6" }, { "id": "MV514-030", "module": "MV-514", "level": "P", "region": "All", "question": "Why is RSTP alone usually not enough for a process bus carrying sampled values?", "options": [ "It does not support Ethernet", "It is too expensive", "Its recovery after a failure takes milliseconds to seconds, and samples are lost meanwhile", "It needs copper cables" ], "answer": 2, "explanation": "PRP and HSR give zero recovery time instead.", "ref": "" }, { "id": "MV514-031", "module": "MV-514", "level": "P", "region": "All", "question": "A device with a single network port must join a PRP network. What is used?", "options": [ "A media converter only", "A router", "A QuadBox", "A RedBox" ], "answer": 3, "explanation": "A redundancy box connects singly attached nodes to both LANs.", "ref": "IEC 62439-3" }, { "id": "MV514-032", "module": "MV-514", "level": "P", "region": "All", "question": "A 1 ms time error between merging units at 50 Hz equals what phase angle error?", "options": [ "0.018 degrees", "18 degrees", "1.8 degrees", "180 degrees" ], "answer": 1, "explanation": "360 x 50 x 0.001 = 18 degrees, enough to cause false differential trips.", "ref": "" }, { "id": "MV514-033", "module": "MV-514", "level": "P", "region": "All", "question": "Which logical node represents a switch controller that handles operator commands and interlocks?", "options": [ "XSWI", "PTRC", "CSWI", "LPHD" ], "answer": 2, "explanation": "CSWI controls, XSWI and XCBR represent the primary equipment.", "ref": "IEC 61850-7-4" }, { "id": "MV514-034", "module": "MV-514", "level": "P", "region": "All", "question": "What is the default TCP port for IEC 60870-5-104?", "options": [ "102", "20000", "2404", "502" ], "answer": 2, "explanation": "IEC 104 uses TCP port 2404.", "ref": "IEC 60870-5-104" }, { "id": "MV514-035", "module": "MV-514", "level": "P", "region": "All", "question": "Which logical node is differential protection?", "options": [ "PTUV", "PDIS", "PDIF", "PTOC" ], "answer": 2, "explanation": "PDIF covers transformer, line and busbar differential functions.", "ref": "IEC 61850-7-4" }, { "id": "MV514-036", "module": "MV-514", "level": "P", "region": "GCC", "question": "What do GCC utilities typically demand alongside IEC 61850 in new substations?", "options": [ "No network security", "Copper-only wiring", "Manual switching only", "Strong cyber security controls aligned with standards such as IEC 62351 and IEC 62443" ], "answer": 3, "explanation": "Cyber security requirements are part of the specification for digital substations in the region.", "ref": "" }, { "id": "MV514-037", "module": "MV-514", "level": "E", "region": "All", "question": "Why is GOOSE not normally routed across IP networks?", "options": [ "It is encrypted by default", "It is too slow", "It is a Layer 2 multicast Ethernet message with no IP header", "It uses serial links" ], "answer": 2, "explanation": "Routable GOOSE and SV are defined separately in IEC 61850-90-5.", "ref": "IEC 61850-8-1" }, { "id": "MV514-038", "module": "MV-514", "level": "E", "region": "All", "question": "What PTP accuracy is generally targeted for protection sampled values?", "options": [ "About 1 nanosecond", "About 1 ms", "About 1 second", "About 1 microsecond" ], "answer": 3, "explanation": "1 microsecond equals about 0.018 degrees at 50 Hz, which is negligible for protection.", "ref": "IEC 61850-9-3" }, { "id": "MV514-039", "module": "MV-514", "level": "E", "region": "All", "question": "How many SV frames per second are sent at 256 samples per cycle on 50 Hz if each frame carries one sample?", "options": [ "12,800", "4,000", "25,600", "5,120" ], "answer": 0, "explanation": "256 x 50 = 12,800.", "ref": "" }, { "id": "MV514-040", "module": "MV-514", "level": "E", "region": "All", "question": "Why are VLANs and priority tagging used for GOOSE and SV?", "options": [ "To replace time sync", "To separate traffic and give trips priority in switch queues", "To encrypt the payload", "To increase the sample rate" ], "answer": 1, "explanation": "IEEE 802.1Q tags keep high-volume SV from delaying critical GOOSE.", "ref": "" }, { "id": "MV514-041", "module": "MV-514", "level": "E", "region": "All", "question": "During testing of a live IED in a digital substation, how is the IED kept from tripping real breakers?", "options": [ "Changing the IP address", "Turning off PTP", "Removing the fibre only", "Using the IEC 61850 test and simulation modes and flags so test messages are not acted on by in-service devices" ], "answer": 3, "explanation": "Test mode and the simulation bit let test GOOSE and SV be isolated from the process.", "ref": "IEC 61850-7-4" }, { "id": "MV514-042", "module": "MV-514", "level": "E", "region": "All", "question": "What is a key cyber security concern with GOOSE in its basic form?", "options": [ "It needs a cloud server", "It has no built-in authentication, so spoofed messages could cause trips", "It is too slow", "It uses too much bandwidth" ], "answer": 1, "explanation": "IEC 62351-6 adds authentication for GOOSE and SV.", "ref": "IEC 62351-6" }, { "id": "MV514-043", "module": "MV-514", "level": "E", "region": "All", "question": "In HSR, which device connects two HSR rings?", "options": [ "QuadBox", "RedBox", "Merging unit", "Gateway" ], "answer": 0, "explanation": "A QuadBox joins two rings while keeping seamless redundancy.", "ref": "IEC 62439-3" }, { "id": "MV514-044", "module": "MV-514", "level": "E", "region": "All", "question": "Why must a merging unit flag the loss of time sync in its SV stream?", "options": [ "To raise the sample rate", "So receiving IEDs can block functions that need aligned samples from several sources", "To restart the network", "To change the frame size" ], "answer": 1, "explanation": "The smpSynch attribute tells the subscriber whether samples are synchronised.", "ref": "IEC 61850-9-2" }, { "id": "MV514-045", "module": "MV-514", "level": "E", "region": "All", "question": "What is the default TCP port for DNP3 over IP?", "options": [ "20000", "2404", "443", "502" ], "answer": 0, "explanation": "DNP3 uses TCP or UDP port 20000.", "ref": "IEEE 1815" }, { "id": "MV514-046", "module": "MV-514", "level": "E", "region": "All", "question": "Why should the SCD file be under version control?", "options": [ "It defines every IED dataset and message, so an untracked change can break protection or interlocking", "It replaces drawings", "It is a legal contract", "It stores alarm logs" ], "answer": 0, "explanation": "It is the master configuration of the automation system.", "ref": "IEC 61850-6" }, { "id": "MV514-047", "module": "MV-514", "level": "E", "region": "NZ", "question": "A New Zealand lines company adds remote-controlled RMUs with fault passage indicators. What main SCADA benefit does this give?", "options": [ "Faster fault location and restoration, which lowers SAIDI", "Higher fault level", "Lower losses", "Fewer transformers" ], "answer": 0, "explanation": "Remote switching and FPIs support FLISR schemes that cut outage minutes.", "ref": "" }, { "id": "MV514-048", "module": "MV-514", "level": "E", "region": "Asia", "question": "Which statement about IEC 61850 in many Asian utilities is accurate?", "options": [ "It is widely used as the standard for new primary substations", "It is used only in LV boards", "It is banned", "It is only used for metering" ], "answer": 0, "explanation": "Many utilities in the region specify IEC 61850 for new primary substation automation.", "ref": "" }, { "id": "MV514-049", "module": "MV-514", "level": "B", "region": "GCC", "question": "What do GCC utilities typically add to 11 kV RMUs for distribution automation?", "options": [ "Larger fuses", "Manual handles only", "Motorised switches, fault passage indicators and an RTU linked to SCADA", "Extra earthing only" ], "answer": 2, "explanation": "Remote control and fault indication let the control centre isolate faults and restore supply quickly.", "ref": "" }, { "id": "MV514-050", "module": "MV-514", "level": "P", "region": "AU", "question": "What does DNP3 Secure Authentication add on Australian and New Zealand telecontrol links?", "options": [ "Higher sample rates", "A check that commands come from an authorised master and were not altered", "Wireless support", "Faster polling" ], "answer": 1, "explanation": "It uses challenge and response so a spoofed control cannot operate field equipment.", "ref": "IEEE 1815" }, { "id": "MV515-001", "module": "MV-515", "level": "B", "region": "All", "question": "What does DGA stand for in transformer maintenance?", "options": [ "Dynamic Grid Analysis", "Dielectric Gap Alignment", "Dissolved Gas Analysis", "Direct Ground Assessment" ], "answer": 2, "explanation": "It measures gases dissolved in insulating oil to detect faults.", "ref": "IEC 60599" }, { "id": "MV515-002", "module": "MV-515", "level": "B", "region": "All", "question": "Which gas most strongly signals arcing in transformer oil?", "options": [ "Carbon dioxide", "Acetylene", "Nitrogen", "Methane" ], "answer": 1, "explanation": "C2H2 forms at very high energy, such as arcing.", "ref": "IEC 60599" }, { "id": "MV515-003", "module": "MV-515", "level": "B", "region": "All", "question": "Which three gases does Duval Triangle 1 use?", "options": [ "CH4, C2H4, C2H2", "H2, CO, CO2", "O2, N2, H2", "C2H6, CO, H2" ], "answer": 0, "explanation": "Methane, ethylene and acetylene, as relative percentages.", "ref": "IEC 60599" }, { "id": "MV515-004", "module": "MV-515", "level": "B", "region": "All", "question": "Hydrogen with little else in oil usually suggests what?", "options": [ "Partial discharge", "Healthy oil", "Overheated paper", "Moisture only" ], "answer": 0, "explanation": "Low energy PD mainly breaks oil into hydrogen.", "ref": "" }, { "id": "MV515-005", "module": "MV-515", "level": "B", "region": "All", "question": "Carbon monoxide and carbon dioxide in oil come mainly from what?", "options": [ "The steel tank", "Copper windings", "Paper insulation (cellulose)", "Silica gel" ], "answer": 2, "explanation": "Heating cellulose produces CO and CO2.", "ref": "" }, { "id": "MV515-006", "module": "MV-515", "level": "B", "region": "All", "question": "In the Duval Triangle 1, what does zone PD mean?", "options": [ "Paper decay", "Power distribution", "Pressure drop", "Partial discharge" ], "answer": 3, "explanation": "PD sits at the methane-rich corner of the triangle.", "ref": "" }, { "id": "MV515-007", "module": "MV-515", "level": "B", "region": "All", "question": "In Duval Triangle 1, zone T3 means what?", "options": [ "Thermal fault above 700 degC", "Thermal fault 300 to 700 degC", "Low energy discharge", "Thermal fault below 300 degC" ], "answer": 0, "explanation": "T1 is below 300, T2 is 300 to 700 and T3 is above 700 degC.", "ref": "" }, { "id": "MV515-008", "module": "MV-515", "level": "B", "region": "All", "question": "In Duval Triangle 1, zone D2 means what?", "options": [ "Partial discharge", "Mixed thermal and electrical", "High energy discharge (arcing)", "Low energy discharge" ], "answer": 2, "explanation": "D1 is low energy sparking, D2 is high energy arcing.", "ref": "" }, { "id": "MV515-009", "module": "MV-515", "level": "B", "region": "All", "question": "In thermography, why compare the three phases of the same termination?", "options": [ "Absolute temperature is always exact", "To avoid emissivity settings", "Similar parts under similar load should be at similar temperature, so a difference shows a problem", "To measure voltage" ], "answer": 2, "explanation": "Comparative delta-T is more reliable than absolute readings.", "ref": "" }, { "id": "MV515-010", "module": "MV-515", "level": "B", "region": "All", "question": "Under NETA guidance for similar components, a delta-T above 15 K is classed as what?", "options": [ "Major discrepancy needing immediate repair", "Probable deficiency", "Normal", "Possible deficiency" ], "answer": 0, "explanation": "1 to 3 K is possible, 4 to 15 K is probable, above 15 K is major.", "ref": "ANSI/NETA MTS" }, { "id": "MV515-011", "module": "MV-515", "level": "B", "region": "All", "question": "Why should thermography be done at high load?", "options": [ "Cameras work better in heat", "Utilities require it for billing", "It reduces emissivity", "Heating rises with current, so low load hides defects" ], "answer": 3, "explanation": "I squared R heating grows quickly with load.", "ref": "" }, { "id": "MV515-012", "module": "MV-515", "level": "B", "region": "All", "question": "What is emissivity in thermography?", "options": [ "How well a surface radiates infrared compared with a perfect black body", "The voltage of the target", "The camera lens size", "The ambient humidity" ], "answer": 0, "explanation": "Shiny metal has low emissivity and reads colder than it really is.", "ref": "" }, { "id": "MV515-013", "module": "MV-515", "level": "B", "region": "All", "question": "What is partial discharge?", "options": [ "A blown fuse", "A full flashover between phases", "A small electrical discharge that only partly bridges the insulation", "A battery fault" ], "answer": 2, "explanation": "PD slowly erodes insulation and often comes before failure.", "ref": "IEC 60270" }, { "id": "MV515-014", "module": "MV-515", "level": "B", "region": "All", "question": "In which unit is apparent partial discharge charge measured under IEC 60270?", "options": [ "Volts", "Lux", "Picocoulombs", "Ohms" ], "answer": 2, "explanation": "Apparent charge is in pC.", "ref": "IEC 60270" }, { "id": "MV515-015", "module": "MV-515", "level": "B", "region": "All", "question": "What does a TEV sensor detect in metal-clad switchgear?", "options": [ "Temperature", "Gas pressure", "Oil level", "Transient earth voltages on the enclosure caused by internal PD" ], "answer": 3, "explanation": "PD pulses couple to the metal panel surface as small voltage transients.", "ref": "" }, { "id": "MV515-016", "module": "MV-515", "level": "B", "region": "All", "question": "Ultrasonic PD detection is best for which kind of discharge?", "options": [ "Discharges deep inside solid insulation", "Earth faults", "Overloads", "Surface tracking and corona in air" ], "answer": 3, "explanation": "Airborne ultrasound picks up surface and corona activity.", "ref": "" }, { "id": "MV515-017", "module": "MV-515", "level": "B", "region": "All", "question": "Furan analysis of transformer oil gives information about what?", "options": [ "Tap changer position", "The ageing of the paper insulation", "Moisture in the tank", "Copper loss" ], "answer": 1, "explanation": "Furans such as 2-FAL come from cellulose breakdown.", "ref": "" }, { "id": "MV515-018", "module": "MV-515", "level": "B", "region": "GCC", "question": "Why are pre-summer thermography surveys especially important in the GCC?", "options": [ "Utilities ban summer work", "Cameras are cheaper in spring", "Dust improves readings", "High ambient temperatures and summer peak loads push weak joints to failure" ], "answer": 3, "explanation": "Finding hot joints before the peak avoids summer failures.", "ref": "" }, { "id": "MV515-019", "module": "MV-515", "level": "B", "region": "NZ", "question": "Why are post-earthquake inspections common for New Zealand substations?", "options": [ "For tax reasons", "Seismic shaking can loosen connections and damage bushings and terminations", "To test batteries", "To read meters" ], "answer": 1, "explanation": "Shaking can disturb connections and equipment mounts.", "ref": "" }, { "id": "MV515-020", "module": "MV-515", "level": "P", "region": "All", "question": "A DGA result gives CH4 60, C2H4 200 and C2H2 4 ppm. Which Duval zone applies?", "options": [ "T2", "T1", "T3", "D1" ], "answer": 2, "explanation": "Percentages are CH4 22.7%, C2H4 75.8%, C2H2 1.5%. C2H4 above 50% with C2H2 below 15% is T3.", "ref": "IEC 60599" }, { "id": "MV515-021", "module": "MV-515", "level": "P", "region": "All", "question": "A DGA result gives CH4 100, C2H4 20 and C2H2 2 ppm. Which Duval zone applies?", "options": [ "T1", "T2", "PD", "D1" ], "answer": 0, "explanation": "CH4 82%, C2H4 16.4%, C2H2 1.6%. C2H4 below 20% and C2H2 below 4% is T1.", "ref": "IEC 60599" }, { "id": "MV515-022", "module": "MV-515", "level": "P", "region": "All", "question": "A DGA result gives CH4 60, C2H4 38 and C2H2 2 ppm. Which Duval zone applies?", "options": [ "D2", "T1", "T3", "T2" ], "answer": 3, "explanation": "Total 100 ppm, so C2H4 38% (20 to 50%) and C2H2 2% (below 4%) is T2.", "ref": "IEC 60599" }, { "id": "MV515-023", "module": "MV-515", "level": "P", "region": "All", "question": "A DGA result gives CH4 10, C2H4 10 and C2H2 80 ppm. Which Duval zone applies?", "options": [ "T1", "T3", "D1", "PD" ], "answer": 2, "explanation": "C2H4 10% (below 23%) with C2H2 80% (above 13%) is D1, low energy discharge.", "ref": "IEC 60599" }, { "id": "MV515-024", "module": "MV-515", "level": "P", "region": "All", "question": "A 6 K delta-T is measured at 50% load. Using an exponent of 2, about what is it at full load?", "options": [ "12 K", "36 K", "6 K", "24 K" ], "answer": 3, "explanation": "6 x (100/50)² = 24 K, which is a major discrepancy.", "ref": "" }, { "id": "MV515-025", "module": "MV-515", "level": "P", "region": "All", "question": "A 5 K delta-T is measured at 70% load. Using an exponent of 2, about what is it at full load, and what class?", "options": [ "About 5 K, possible", "About 10 K, probable", "About 7 K, possible", "About 20 K, major" ], "answer": 1, "explanation": "5 / 0.7² = 10.2 K, in the 4 to 15 K probable band.", "ref": "" }, { "id": "MV515-026", "module": "MV-515", "level": "P", "region": "All", "question": "A 3 K delta-T is measured at 40% load. Using an exponent of 2, what is it at full load?", "options": [ "About 7.5 K", "About 18.8 K", "About 30 K", "About 12 K" ], "answer": 1, "explanation": "3 x (1/0.4)² = 18.75 K, above 15 K so major.", "ref": "" }, { "id": "MV515-027", "module": "MV-515", "level": "P", "region": "All", "question": "A bright, bare aluminium lug is measured with emissivity set to 0.95. What happens?", "options": [ "The camera cannot focus", "It reads hotter than reality", "It reads colder than reality", "It reads exactly right" ], "answer": 2, "explanation": "Low emissivity surfaces emit less IR, so a high setting understates the temperature.", "ref": "" }, { "id": "MV515-028", "module": "MV-515", "level": "P", "region": "All", "question": "A CO2 to CO ratio below about 3 suggests what?", "options": [ "Overheating involving the paper insulation", "Arcing in oil only", "Air leak", "Healthy paper" ], "answer": 0, "explanation": "A low ratio points to cellulose being degraded by heat.", "ref": "IEC 60599" }, { "id": "MV515-029", "module": "MV-515", "level": "P", "region": "All", "question": "What degree of polymerisation (DP) is typical of new transformer paper?", "options": [ "About 50", "About 1,000 to 1,200", "About 200", "About 10,000" ], "answer": 1, "explanation": "New kraft paper is around 1,000 to 1,200. Near 200 the paper is close to end of life.", "ref": "" }, { "id": "MV515-030", "module": "MV-515", "level": "P", "region": "All", "question": "Paper with a DP of about 200 means what?", "options": [ "Brand new insulation", "Thermally upgraded paper only", "Moisture-free paper", "Paper near end of mechanical life" ], "answer": 3, "explanation": "At this level the paper has lost most of its mechanical strength.", "ref": "" }, { "id": "MV515-031", "module": "MV-515", "level": "P", "region": "All", "question": "On a PRPD plot, an internal void usually shows what pattern?", "options": [ "Pulses only at the negative peak", "Roughly symmetric clusters on the rising parts of both half cycles", "A flat line at zero phase", "No pulses at all" ], "answer": 1, "explanation": "Voids discharge on both polarities, usually ahead of the voltage peaks.", "ref": "" }, { "id": "MV515-032", "module": "MV-515", "level": "P", "region": "All", "question": "On a PRPD plot, corona from a sharp point at high voltage usually appears where?", "options": [ "Only at zero crossing", "Mainly around the negative voltage peak", "Spread over all phase angles randomly", "Equally on both half cycles" ], "answer": 1, "explanation": "Negative corona starts at a lower voltage, so pulses group near the negative peak.", "ref": "" }, { "id": "MV515-033", "module": "MV-515", "level": "P", "region": "All", "question": "Why is a single DGA result less useful than a trend?", "options": [ "Labs are always wrong", "Rate of increase shows whether a fault is active, while one value may be background gas", "Gases do not change", "Standards ban single tests" ], "answer": 1, "explanation": "IEC 60599 and IEEE C57.104 use both levels and rates of increase.", "ref": "IEEE C57.104" }, { "id": "MV515-034", "module": "MV-515", "level": "P", "region": "All", "question": "Which sensor is commonly clamped on a cable earth screen to detect PD?", "options": [ "Pressure gauge", "HFCT (high frequency current transformer)", "Thermocouple", "Hygrometer" ], "answer": 1, "explanation": "An HFCT picks up PD pulses travelling on the screen.", "ref": "" }, { "id": "MV515-035", "module": "MV-515", "level": "P", "region": "All", "question": "Why should Duval Triangle 1 not be applied to very low gas levels?", "options": [ "It only works above 10,000 ppm", "Normal background gases can plot into a fault zone and give a false diagnosis", "The triangle needs oxygen", "The maths fails" ], "answer": 1, "explanation": "Use it when gases exceed typical values or are rising.", "ref": "IEC 60599" }, { "id": "MV515-036", "module": "MV-515", "level": "P", "region": "Asia", "question": "In tropical Asian cable networks, what commonly contributes to termination failures?", "options": [ "Low ambient temperature", "Excessive dryness", "Snow loading", "High humidity and moisture ingress causing surface tracking" ], "answer": 3, "explanation": "Moisture and contamination drive surface discharges on terminations.", "ref": "" }, { "id": "MV515-037", "module": "MV-515", "level": "E", "region": "All", "question": "In Duval Triangle 1, what does zone DT mean?", "options": [ "Dielectric test result", "A mix of thermal and electrical faults", "Dry type transformer", "Pure thermal fault" ], "answer": 1, "explanation": "DT sits between thermal and discharge zones.", "ref": "IEC 60599" }, { "id": "MV515-038", "module": "MV-515", "level": "E", "region": "All", "question": "Which tools help separate overlapping thermal faults after Duval Triangle 1?", "options": [ "A megger", "Duval Triangles 4 and 5 and the Duval Pentagons", "A power quality meter", "A clamp meter" ], "answer": 1, "explanation": "They use additional gases such as H2 and C2H6 to refine the diagnosis.", "ref": "" }, { "id": "MV515-039", "module": "MV-515", "level": "E", "region": "All", "question": "A cable termination shows rising PD for six months, then a surface flashover. What root cause category is most often found?", "options": [ "Overvoltage from the utility", "Lightning only", "Installation workmanship such as poor stress control or contamination", "Manufacturing design flaw" ], "answer": 2, "explanation": "Many MV failures trace back to workmanship and moisture.", "ref": "" }, { "id": "MV515-040", "module": "MV-515", "level": "E", "region": "All", "question": "After an MV failure, what should be done first in the investigation?", "options": [ "Blame the manufacturer", "Make it safe, then preserve and record the evidence before disturbing it", "Clean the site and replace parts quickly", "Re-energise to see if it fails again" ], "answer": 1, "explanation": "Photos, positions and samples are lost once the area is cleaned.", "ref": "" }, { "id": "MV515-041", "module": "MV-515", "level": "E", "region": "All", "question": "Which method structures a root cause analysis by asking why repeatedly?", "options": [ "Gantt chart", "Pareto chart only", "Single line diagram", "Five whys" ], "answer": 3, "explanation": "Five whys, often with a fishbone diagram, moves past symptoms to causes.", "ref": "" }, { "id": "MV515-042", "module": "MV-515", "level": "E", "region": "All", "question": "A transformer shows rising acetylene but stable other gases. What is the correct response?", "options": [ "Treat it as urgent, increase sampling and investigate possible arcing, including the tap changer if it shares oil", "Ignore it until other gases rise", "Raise the loading", "Top up the oil" ], "answer": 0, "explanation": "Any new or rising acetylene needs prompt attention.", "ref": "IEC 60599" }, { "id": "MV515-043", "module": "MV-515", "level": "E", "region": "All", "question": "Why do some guides use an exponent of about 1.6 rather than 2 for thermographic load correction?", "options": [ "Heat loss by convection and radiation does not scale exactly with I squared R, so 1.6 is a conservative estimate", "It removes emissivity error", "Cameras need it", "It is required by law" ], "answer": 0, "explanation": "2 assumes pure I squared R behaviour, lower exponents give a more cautious extrapolation.", "ref": "" }, { "id": "MV515-044", "module": "MV-515", "level": "E", "region": "All", "question": "Which is a known cause of hydrogen in oil that is not a fault?", "options": [ "Arcing on the tap changer", "Core earth fault", "Paper overheating", "Stray gassing of some oils at moderate temperatures" ], "answer": 3, "explanation": "Some oils generate H2 and other gases at normal service temperatures.", "ref": "IEC 60599" }, { "id": "MV515-045", "module": "MV-515", "level": "E", "region": "All", "question": "A surface tracking PRPD pattern is usually what compared with an internal void?", "options": [ "Identical", "Only at zero crossing", "Perfectly symmetric", "Asymmetric between half cycles, with different pulse sizes on each polarity" ], "answer": 3, "explanation": "Surface discharges often show unequal positive and negative clusters.", "ref": "" }, { "id": "MV515-046", "module": "MV-515", "level": "E", "region": "AU", "question": "How do Australian distributors commonly manage zone substation transformers?", "options": [ "Replacement every 5 years", "No testing", "Condition-based maintenance using DGA and online monitoring", "Run to failure only" ], "answer": 2, "explanation": "Condition data drives maintenance and replacement priorities.", "ref": "" }, { "id": "MV515-047", "module": "MV-515", "level": "P", "region": "GCC", "question": "In coastal GCC substations, what mainly drives surface tracking on cable terminations?", "options": [ "Low load", "High altitude", "Snow", "Humidity combined with salt and dust deposits" ], "answer": 3, "explanation": "Contaminated, damp surfaces carry leakage current that starts tracking.", "ref": "" }, { "id": "MV515-048", "module": "MV-515", "level": "B", "region": "KSA", "question": "Why does high summer ambient temperature in Saudi Arabia call for closer transformer condition monitoring?", "options": [ "It stops partial discharge", "It lowers the load", "It removes gases from oil", "It raises the winding hot spot temperature, which speeds up paper ageing" ], "answer": 3, "explanation": "Paper ageing roughly doubles for every 6 to 7 K rise in hot spot temperature.", "ref": "IEC 60076-7" }, { "id": "MV515-049", "module": "MV-515", "level": "E", "region": "NZ", "question": "After an earthquake, which DGA change on a New Zealand zone substation transformer would most need urgent follow-up?", "options": [ "No change in any gas", "A stable CO2 level", "A slightly lower oxygen level", "New or rising acetylene" ], "answer": 3, "explanation": "Acetylene after shaking can indicate internal movement causing arcing.", "ref": "IEC 60599" }, { "id": "MV515-050", "module": "MV-515", "level": "P", "region": "AU", "question": "What is a common use of online PD monitoring in Australian zone substations?", "options": [ "Measuring tariffs", "Trending insulation condition of switchgear and cables so repairs can be planned", "Billing", "Controlling tap changers" ], "answer": 1, "explanation": "Trends give months of warning before many failures.", "ref": "" }, { "id": "MV516-001", "module": "MV-516", "level": "B", "region": "All", "question": "What sizes the transformers for a building?", "options": [ "Maximum demand with growth and planned loading", "Total connected load", "The room height", "The cable route length" ], "answer": 0, "explanation": "Diversity converts connected load into maximum demand.", "ref": "" }, { "id": "MV516-002", "module": "MV-516", "level": "B", "region": "All", "question": "What does N+1 transformer redundancy mean?", "options": [ "A single large unit", "Double the number needed", "One spare unit beyond what the load needs", "One fewer unit than the load needs" ], "answer": 2, "explanation": "Supply survives the loss of any one transformer.", "ref": "" }, { "id": "MV516-003", "module": "MV-516", "level": "B", "region": "All", "question": "What is a demand factor?", "options": [ "The cable derating", "The power factor", "Maximum demand of a load divided by its connected load", "Voltage divided by current" ], "answer": 2, "explanation": "It is always 1 or less for a single load group.", "ref": "" }, { "id": "MV516-004", "module": "MV-516", "level": "B", "region": "All", "question": "What is a diversity factor used for in load estimates?", "options": [ "To increase cable size", "To calculate fault level", "To allow for not all loads peaking at the same time", "To set the vector group" ], "answer": 2, "explanation": "Group peaks do not coincide, so the total maximum demand is lower.", "ref": "" }, { "id": "MV516-005", "module": "MV-516", "level": "B", "region": "All", "question": "In a typical CCF RMU for a building substation, what does the F panel feed?", "options": [ "The distribution transformer, through a fuse switch or circuit breaker", "The incoming ring cable", "The earthing system", "The LV main switchboard directly" ], "answer": 0, "explanation": "C panels are ring cable switches and the F panel protects and switches the transformer feeder.", "ref": "IEC 62271-200" }, { "id": "MV516-006", "module": "MV-516", "level": "B", "region": "All", "question": "Above roughly which transformer size do RMU feeders usually move from fuse-switches to circuit breakers?", "options": [ "630 kVA", "315 kVA", "5,000 kVA", "1,000 to 1,250 kVA" ], "answer": 3, "explanation": "Fuses become hard to coordinate and rate above this size.", "ref": "" }, { "id": "MV516-007", "module": "MV-516", "level": "B", "region": "All", "question": "Which standard is used to calculate cable current ratings?", "options": [ "IEC 61850", "IEC 62351", "IEC 60287", "IEC 60599" ], "answer": 2, "explanation": "IEC 60287 covers current rating and derating calculations.", "ref": "IEC 60287" }, { "id": "MV516-008", "module": "MV-516", "level": "B", "region": "All", "question": "What is a BOQ?", "options": [ "Bill of Quantities listing items, quantities and rates", "Basic Operating Quote", "Breaker Operating Quality", "Building Ownership Questionnaire" ], "answer": 0, "explanation": "The BOQ links the design to the cost estimate.", "ref": "" }, { "id": "MV516-009", "module": "MV-516", "level": "B", "region": "All", "question": "What is the critical path in a programme?", "options": [ "The shortest chain of tasks", "Any task with a cost", "The longest chain of dependent tasks, which sets the finish date", "The utility's route" ], "answer": 2, "explanation": "A delay on the critical path delays the whole project.", "ref": "" }, { "id": "MV516-010", "module": "MV-516", "level": "B", "region": "All", "question": "Which items are commonly long-lead for a substation?", "options": [ "Paint", "Door handles", "Transformers, RMUs and LV main boards", "Light switches" ], "answer": 2, "explanation": "Track them from the first design stage.", "ref": "" }, { "id": "MV516-011", "module": "MV-516", "level": "B", "region": "All", "question": "A 30,000 m² hotel at 80 W/m² has what connected load estimate?", "options": [ "2,400 kW", "240 kW", "24,000 kW", "800 kW" ], "answer": 0, "explanation": "30,000 x 80 = 2,400,000 W = 2,400 kW.", "ref": "" }, { "id": "MV516-012", "module": "MV-516", "level": "B", "region": "All", "question": "Why are example cost rates in a simulator not used directly for a tender?", "options": [ "They are always too high", "Rates are fixed by law", "Tenders do not use costs", "They are placeholders and must be replaced with current quotes or a cost database" ], "answer": 3, "explanation": "Market prices change and vary by region and supplier.", "ref": "" }, { "id": "MV516-013", "module": "MV-516", "level": "B", "region": "KSA", "question": "Which MV distribution voltage and frequency are common in Saudi cities?", "options": [ "13.8 kV at 60 Hz", "22 kV at 50 Hz", "11 kV at 50 Hz", "33 kV at 50 Hz" ], "answer": 0, "explanation": "Saudi Arabia runs at 60 Hz with 13.8 kV widely used for distribution.", "ref": "" }, { "id": "MV516-014", "module": "MV-516", "level": "B", "region": "GCC", "question": "In many GCC projects, who often supplies the RMU and transformers?", "options": [ "The insurer", "The tenant", "The utility, so the developer scope may be the room, LV board and connection charges", "The architect" ], "answer": 2, "explanation": "Check the utility scope split early because it changes the BOQ.", "ref": "" }, { "id": "MV516-015", "module": "MV-516", "level": "B", "region": "AU", "question": "In Australia, what are contestable works?", "options": [ "Disputed invoices", "Connection works that accredited contractors may build and hand over to the distributor", "Temporary lighting", "Works the utility must always build" ], "answer": 1, "explanation": "The developer scope can then include MV equipment and cables.", "ref": "" }, { "id": "MV516-016", "module": "MV-516", "level": "B", "region": "Asia", "question": "What is the main MV distribution voltage in Singapore?", "options": [ "11 kV", "33 kV", "66 kV", "22 kV" ], "answer": 3, "explanation": "SP Group distributes mainly at 22 kV, with 6.6 kV in some areas.", "ref": "" }, { "id": "MV516-017", "module": "MV-516", "level": "B", "region": "All", "question": "What must the substation room design allow for besides equipment space?", "options": [ "Only paint colour", "Access, ventilation, fire rating and maintenance clearances", "Only lighting", "Only the door colour" ], "answer": 1, "explanation": "IEC 61936-1 sets requirements for installations above 1 kV.", "ref": "IEC 61936-1" }, { "id": "MV516-018", "module": "MV-516", "level": "B", "region": "All", "question": "Why is the substation location frozen early with the architect and utility?", "options": [ "It sets the building height", "It sets the cable routes, access and room design that many later steps depend on", "It changes the voltage", "It sets the tariff" ], "answer": 1, "explanation": "Late moves ripple through civil, MV and LV design.", "ref": "" }, { "id": "MV516-019", "module": "MV-516", "level": "B", "region": "NZ", "question": "In Auckland, which lines company owns most of the distribution network?", "options": [ "Orion", "Wellington Electricity", "Transpower", "Vector" ], "answer": 3, "explanation": "Vector is the distribution company for most of Auckland.", "ref": "" }, { "id": "MV516-020", "module": "MV-516", "level": "P", "region": "All", "question": "A 30,000 m² hotel at 80 W/m², diversity 0.75, power factor 0.9 and 15% growth gives what design demand?", "options": [ "1,800 kVA", "2,300 kVA", "2,760 kVA", "2,000 kVA" ], "answer": 1, "explanation": "2,400 x 0.75 = 1,800 kW, / 0.9 = 2,000 kVA, x 1.15 = 2,300 kVA.", "ref": "" }, { "id": "MV516-021", "module": "MV-516", "level": "P", "region": "All", "question": "For a 2,300 kVA demand using 1,500 kVA transformers at 80% maximum loading, how many units are needed with N+1?", "options": [ "4", "5", "3", "2" ], "answer": 2, "explanation": "Each unit carries 1,200 kVA, so 2 are needed (2,400 kVA). N+1 gives 3.", "ref": "" }, { "id": "MV516-022", "module": "MV-516", "level": "P", "region": "All", "question": "What is the full load current of a 1,500 kVA transformer on the 11 kV side?", "options": [ "About 45 A", "About 79 A", "About 136 A", "About 2,165 A" ], "answer": 1, "explanation": "1,500 / (1.732 x 11) = 78.7 A.", "ref": "" }, { "id": "MV516-023", "module": "MV-516", "level": "P", "region": "All", "question": "What is the full load current of a 1,500 kVA transformer at 400 V?", "options": [ "About 1,443 A", "About 866 A", "About 3,750 A", "About 2,165 A" ], "answer": 3, "explanation": "1,500,000 / (1.732 x 400) = 2,165 A.", "ref": "" }, { "id": "MV516-024", "module": "MV-516", "level": "P", "region": "All", "question": "A 1,000 kVA transformer at 400 V has what full load current?", "options": [ "About 1,443 A", "About 577 A", "About 1,000 A", "About 2,500 A" ], "answer": 0, "explanation": "1,000,000 / (1.732 x 400) = 1,443 A.", "ref": "" }, { "id": "MV516-025", "module": "MV-516", "level": "P", "region": "All", "question": "A 1,500 kVA, 400 V transformer has 6% impedance. Ignoring source impedance, what is the LV fault level?", "options": [ "About 36 kA", "About 21 kA", "About 48 kA", "About 90 kA" ], "answer": 0, "explanation": "2,165 / 0.06 = 36.1 kA.", "ref": "" }, { "id": "MV516-026", "module": "MV-516", "level": "P", "region": "All", "question": "A 2,000 kVA, 400 V transformer has 6% impedance. Ignoring source impedance, what is the LV fault level?", "options": [ "About 36 kA", "About 33 kA", "About 48 kA", "About 60 kA" ], "answer": 2, "explanation": "2,887 / 0.06 = 48.1 kA.", "ref": "" }, { "id": "MV516-027", "module": "MV-516", "level": "P", "region": "All", "question": "A ring must carry 6 MVA at 11 kV fed from one end. What current is that?", "options": [ "About 630 A", "About 315 A", "About 545 A", "About 157 A" ], "answer": 1, "explanation": "6,000 / (1.732 x 11) = 315 A.", "ref": "" }, { "id": "MV516-028", "module": "MV-516", "level": "P", "region": "All", "question": "A cable rated 400 A has derating factors of 0.9 for soil and 0.85 for grouping. What is the derated current?", "options": [ "340 A", "400 A", "306 A", "360 A" ], "answer": 2, "explanation": "400 x 0.9 x 0.85 = 306 A.", "ref": "IEC 60287" }, { "id": "MV516-029", "module": "MV-516", "level": "P", "region": "All", "question": "Which factors usually derate a buried MV cable?", "options": [ "Soil thermal resistivity, ground temperature, depth and grouping", "Drum size", "Cable colour", "Sheath printing" ], "answer": 0, "explanation": "Each one reduces how well heat escapes from the cable.", "ref": "IEC 60287" }, { "id": "MV516-030", "module": "MV-516", "level": "P", "region": "All", "question": "A route of 600 m carries two ring circuits of single-core cable in trefoil. How much single-core cable is needed, before allowances?", "options": [ "1,200 m", "1,800 m", "600 m", "3,600 m" ], "answer": 3, "explanation": "2 circuits x 3 cores x 600 m = 3,600 m.", "ref": "" }, { "id": "MV516-031", "module": "MV-516", "level": "P", "region": "All", "question": "Design takes 4 weeks. Then approval 8 weeks and installation 3 weeks follow on one path, while transformer delivery takes 14 weeks after design on another, also followed by installation. What is the critical path length?", "options": [ "21 weeks", "29 weeks", "18 weeks", "15 weeks" ], "answer": 0, "explanation": "Approval path: 4 + 8 + 3 = 15. Transformer path: 4 + 14 + 3 = 21 weeks, so the transformer path is critical.", "ref": "" }, { "id": "MV516-032", "module": "MV-516", "level": "P", "region": "All", "question": "What is float in a programme?", "options": [ "The time a task can slip without delaying the project finish", "A floating floor", "Extra budget", "The cable slack" ], "answer": 0, "explanation": "Critical path tasks have zero float.", "ref": "" }, { "id": "MV516-033", "module": "MV-516", "level": "P", "region": "GCC", "question": "Why do GCC cable ratings often come out lower than in temperate countries?", "options": [ "Shorter routes", "Different copper", "Higher ground temperatures and dry soils with high thermal resistivity", "Lower voltages" ], "answer": 2, "explanation": "Hot, dry ground removes heat poorly, so the rating falls.", "ref": "IEC 60287" }, { "id": "MV516-034", "module": "MV-516", "level": "P", "region": "NZ", "question": "In New Zealand, who usually sets the technical requirements for a new building MV connection?", "options": [ "Transpower for every building", "The building consent authority only", "The retailer", "The local lines company" ], "answer": 3, "explanation": "The distribution lines company sets connection standards and approvals.", "ref": "" }, { "id": "MV516-035", "module": "MV-516", "level": "P", "region": "All", "question": "A transformer has 2 kW no-load loss. At 0.10 per kWh, what does it cost per year?", "options": [ "About 175", "About 876", "About 1,752", "About 17,520" ], "answer": 2, "explanation": "2 x 8,760 x 0.10 = 1,752 per year in any currency unit.", "ref": "" }, { "id": "MV516-036", "module": "MV-516", "level": "E", "region": "All", "question": "A transformer room has 15 kW of losses and the allowed air temperature rise is 10 K. Taking air heat capacity as about 1.2 kJ/m³K, what airflow is needed?", "options": [ "0.8 m³/s", "1.25 m³/s", "12.5 m³/s", "0.125 m³/s" ], "answer": 1, "explanation": "Q = 15 / (1.2 x 10) = 1.25 m³/s.", "ref": "" }, { "id": "MV516-037", "module": "MV-516", "level": "E", "region": "All", "question": "For an MV cable with copper conductor and XLPE (k = 143), what minimum size withstands 20 kA for 1 s?", "options": [ "120 mm²", "95 mm²", "240 mm²", "150 mm²" ], "answer": 3, "explanation": "S = I x sqrt(t) / k = 20,000 / 143 = 140 mm², so choose 150 mm².", "ref": "IEC 60949" }, { "id": "MV516-038", "module": "MV-516", "level": "E", "region": "All", "question": "Why can the present value of transformer losses justify a more expensive unit?", "options": [ "Over 25 years, lost energy can cost about as much as the purchase price", "Utilities pay the losses", "It changes the vector group", "Losses are free" ], "answer": 0, "explanation": "Capitalised loss evaluation adds lifetime energy cost to the price.", "ref": "" }, { "id": "MV516-039", "module": "MV-516", "level": "E", "region": "All", "question": "N+1 with three 1,500 kVA units at 80% planned loading gives what firm capacity?", "options": [ "3,600 kVA", "2,400 kVA", "1,200 kVA", "4,500 kVA" ], "answer": 1, "explanation": "With one unit out, two remain at 1,200 kVA each, giving 2,400 kVA.", "ref": "" }, { "id": "MV516-040", "module": "MV-516", "level": "E", "region": "All", "question": "Why can paralleling LV transformers raise a design problem?", "options": [ "It removes earthing", "It lowers the fault level", "It changes the frequency", "It roughly adds the fault contributions, which can exceed the LV board rating" ], "answer": 3, "explanation": "Two 1,500 kVA units at 6% in parallel give about 72 kA at the LV bus.", "ref": "" }, { "id": "MV516-041", "module": "MV-516", "level": "E", "region": "All", "question": "A late change raises the load by 30%. Which chain is most likely affected?", "options": [ "Only the lighting layout", "Transformer number or size, RMU feeders, LV board, room size and possibly the programme", "Nothing, because of growth allowance", "Only the paint specification" ], "answer": 1, "explanation": "Early decisions ripple through every later step.", "ref": "" }, { "id": "MV516-042", "module": "MV-516", "level": "E", "region": "All", "question": "Which cost items are often a large share of a substation budget but set by the utility?", "options": [ "Labels", "Cable ties", "Paint and signage", "Connection charges and fees" ], "answer": 3, "explanation": "Utility charges should be confirmed early, as they can dominate the estimate.", "ref": "" }, { "id": "MV516-043", "module": "MV-516", "level": "E", "region": "All", "question": "In a 4D model, what is linked to the 3D elements?", "options": [ "Only cable sizes", "Only colours", "Programme dates, so the build sequence can be played over time", "Only cost rates" ], "answer": 2, "explanation": "4D adds time to the 3D model, 5D adds cost.", "ref": "" }, { "id": "MV516-044", "module": "MV-516", "level": "E", "region": "All", "question": "A utility approval slips by 6 weeks on a path with 2 weeks of float. What happens to energisation?", "options": [ "Delayed by 6 weeks", "Delayed by 8 weeks", "Delayed by about 4 weeks", "No delay" ], "answer": 2, "explanation": "The first 2 weeks are absorbed by float, the remaining 4 weeks delay the finish.", "ref": "" }, { "id": "MV516-045", "module": "MV-516", "level": "E", "region": "AU", "question": "Why may an Australian developer BOQ include MV cable and switchgear, unlike many GCC projects?", "options": [ "Cables are free", "MV is not used in Australia", "Australian utilities do not own networks", "Contestable works let the developer engage accredited contractors to build the network assets" ], "answer": 3, "explanation": "Scope splits differ, so the BOQ must follow the local model.", "ref": "" }, { "id": "MV516-046", "module": "MV-516", "level": "E", "region": "Asia", "question": "What should be confirmed early on an Asian substation project because it varies by utility?", "options": [ "The colour of the RMU", "The day of the week for testing", "Whether the utility or the developer supplies the switchgear and transformers", "The font on labels" ], "answer": 2, "explanation": "Scope splits and charges vary between Asian utilities.", "ref": "" }, { "id": "MV516-047", "module": "MV-516", "level": "B", "region": "GCC", "question": "At what MV level does DEWA typically supply building substations in Dubai?", "options": [ "6.6 kV", "132 kV", "33 kV", "11 kV" ], "answer": 3, "explanation": "DEWA distributes at 11 kV from 132/11 kV substations.", "ref": "" }, { "id": "MV516-048", "module": "MV-516", "level": "P", "region": "AU", "question": "For a building in Australia, which standard sets the LV wiring rules that the substation LV side must also meet?", "options": [ "BS 7671", "IEEE 1547", "AS/NZS 3000", "IEC 61850" ], "answer": 2, "explanation": "AS/NZS 3000 is the Wiring Rules for Australia and New Zealand.", "ref": "AS/NZS 3000" } ]