Global MEP Virtual Lab

Design Basis & Authority Workflow

Pick a utility, set the building, and watch the load, transformers, substation, fault levels and approval path update live. Concept-stage thumb rules for load requisitions and early coordination.

LV system

Frequency

Utility MV

Cooling factor

Beginner mode: just pick the region, building type, area and floors. Everything else uses proven defaults. Tap any i for a plain-language explanation.

Expert mode: every engineering assumption is open for editing. Use Reset to go back to the defaults.

Max demand

Transformers

Isc @ LV terminals

Voltage drop to DB

Life safety genset

Try a Real DEWA-Approved Project

Item	This lab (live)	DEWA approved	Difference

Project names, plots and approval numbers removed. Change any input and the lab column updates, so you can see which assumption moves the result.

Building

Building type

Number of floors

Above ground: ground, mezzanine, podium and typical floors.

Basement levels

AUTO

Typical floor plate AUTO

Calculated: (GFA - car park) ÷ floors. Nothing to enter.

Air-conditioned area:

Default for this building type (car parks, plant rooms and shafts are not cooled). Change it in Expert mode if needed.

Hotel Facilities

Restaurants & kitchens In-house laundry Pool, spa & gym

Lighting

Lighting power density (W/m²)

HVAC Cooling Thumb Rule

Cooling source

Area per TR:

Electrical input:

Whole system: chillers, pumps, towers and air-side fans. COP = 3.517 / (kW/TR).

TR = Conditioned area / (m²/TR) → HVAC kW = TR x kW/TR =

Auxiliary Loads

Small power:

Pumps (water transfer, booster, drainage):

Other special loads, kW (EV chargers, data room...)

Retail tenant allowance:

Vertical transportation matrix

Type	Qty	Capacity	Speed	kW each	Total kW

Life safety loads (fire mode)

Include life safety in normal maximum demand

Usually fed from the essential bus with generator backup and left out of normal MD, since fire mode and full building load do not coincide.

Diversity & Maximum Demand

Typical diversity factors for this building type and a 0.90 power factor are applied. Switch to Expert mode to adjust.

Design power factor:

Group	Conn. kW	DF	Demand kW

Total (TCL / MD)

MD (kVA) = Σ(kW x DF) / PF =

Demand Load Share

Connected vs Demand

Transformer Allocation

Standard rating (kVA)

Spare / growth factor:

Max continuous loading cap:

N+1 redundancy (standby transformer)

N = ⌈MD x / S⌉
= ⌈⌉ =
Loading-cap check: ⌈MD / (S x )⌉ =
Duty units = ( governs), total =

Duty transformer loading

Single Line Diagram (live)

Energized

Substation Space Sizing

RMU room

LV room (MLVB line-up)
Total substation footprint
Clear height
Cable trench depth
MV current per transformer

Basis: ~42 m² for 2 x 1500 kVA plus ~22 m² per extra unit, scaled for 1000 / 2000 kVA. Final sizes follow the utility standard substation drawings.

Substation Plan (2D, to scale)

Short-Circuit at Transformer

Impedance Z%

MV fault level (MVA)

Nominal LV voltage (V L-L)

I_rated = S / (√3 x V) =
I_sc (infinite bus) = I_rated / Z =
I_sc (with source) = I_rated / (Z + S/S_sc) =
i_pk = n x I_sc = (IEC 60947-2)

Isc rms

Incomer

Voltage Drop Cascade: Transformer to Final DB

ΔV (%) = √3 x I x L x (R cosθ + X sinθ) / V_LL x 100, cosθ =

Earth Fault Loop Impedance (Zs) & ADS Check

Ze = Z_tx + Z_MV = | Zs = Ze + Σ(R1 + R2) | ADS when Zs ≤ x U0 / Ia, U0 = V

Riser ACB short-time (x In)

DB feeder MCCB magnetic (x In)

Final MCB rating (A)

MCB curve

Point	Protective device	Earth path	Zs	Earth fault I	Ia to trip	Max Zs	Time	Status

Fix options: shorten the circuit, upsize the CPC or the phase conductor, use a lower magnetic setting or Type B MCB, or add RCD / earth fault (G) protection so disconnection no longer depends on overcurrent devices.

TN-S system from the building transformer (Dyn11). Separate Cu CPC sized to BS 7671 Table 54.7, busduct with integral PE bar. Resistances at 90°C operating temperature (conservative). Final circuit 2.5/1.5 mm² with R1+R2 = 19.51 mΩ/m x 1.20. The riser ACB earth fault (G) function and 30 mA RCDs on final circuits give extra margin.

Level 1

Main LV Switchboard (MLVB)

sections, Form 4 Type 6, IEC 61439-2
Incomer:
Bus coupler:
Riser feeders:
APFC:
Plant feeders (HVAC, lifts, pumps):

Level 2

Busbar Risers / SMDBs

x (IEC 61439-6)
Riser current:
Tap-off per floor:
Fault level at riser:
Floor load total:
Neutral:
Plant SMDBs: HVAC, lifts, pumps, life safety (essential)

Level 3

Final Distribution Boards

DBs ( per floor)
Incomer:
DB design current:
Fault level at DB:
Final circuits:

Harmonics & Neutral Sizing Check

Non-linear source (riser fed)	Demand kW	3rd harm.

Weighted

Location	Phase I	Neutral I	Size cable on

LED driver quality

Small power 3rd harmonic:

HVAC plant on VFDs:

VFD / drive harmonics

Basis: BS 7671 Appendix 4 Table 4Aa / IEC 60364-5-52 Annex E. Neutral current = 3 x third-harmonic current. Six-pulse VFDs mainly produce 5th and 7th harmonics, so they distort voltage but do not add neutral current.

Cascade Schedule

Level	Equipment	Protective device	Σ ΔV
L0		RMU T-off (fuse / VCB)	0.00%
L1	MLVB (IEC 61439-2)
L2
L3	Final DB

Approval Path:

Click a step for portals, documents and durations. Press play to run the 4D timeline.

Programme start date

Construction before inspection (months)

Target energization

Timeline position:

Indicative durations using typical ranges and a regional factor. Bars show target calendar dates from the start date above.

Portal / agency (typical)

Submittal checklist

5D CAPEX Estimate

Total electrical distribution CAPEX

Per kVA of MD

Installation & testing:

Contingency:

Bill of Quantities (auto from the design)

Item	Qty	Unit	Rate	Amount

Supply subtotal

Placeholder benchmark rates for concept CAPEX only, not tender prices. Replace them with your own supplier or tender rates in Expert mode. In some GCC utilities the transformers and RMUs are supplied by the utility against connection charges, so remove those lines if they are not in your scope.

Switch to Expert mode to enter your own unit rates.

Design Basis Summary

Ready to paste into a load requisition cover note or design basis report.