Engineer's Notes: approvals and energisation
Start the application early
The utility's supply offer decides whether you need a substation, where it goes and how big it is. Waiting until the design is finished risks redesigning the ground floor.
Consistency gets approvals
Reviewers check the load schedule, SLD, layouts and substation drawings against each other. Matching totals, cable sizes and equipment ratings across every sheet is the fastest route to approval.
The room is on the critical path
The utility cannot install its cables and equipment until the substation room is built, inspected and handed over. A late room pushes back every step after it.
Energise by the book
Energisation day is a switching operation: permits cleared, earths removed, a written program, and each step checked before the next. Rushing it is how new installations get damaged on their first day.
Frequently asked questions
How is maximum demand estimated for a utility load application?
List the connected load by group, multiply each by a demand factor and divide by its power factor to get kVA, add the groups and apply a diversity factor between groups. Use the utility's own demand factors where it publishes them.
When does a building need an HV supply instead of LV?
When the maximum demand is above the limit the utility can supply from its LV network. The limit differs by utility and location, so check it early: an HV supply needs a substation room or kiosk on site, which affects the architecture.
What usually delays energisation?
Late substation room handover, long-lead equipment, missing or inconsistent submission documents, and inspection or witness dates booked too late. The critical path usually runs through the room handover and the utility's own cable works.
What must be done before a new substation is energised?
All tests complete and accepted, earthing connected, labels and SLD in place, keys handed over, protection settings applied and tested, an approved switching program, and every permit to work cleared and cancelled.
What is the correct order to energise a new transformer and LV board?
Clear all personnel and cancel permits, remove earths, energise the RMU, check indicators and phasing, energise the transformer on no load, check LV voltage and phase rotation, close the LV incomer, then close outgoing feeders one at a time and record the readings.
Topics: load application · NOC · maximum demand · demand factor · diversity · transformer sizing · LV or HV supply · connection offer · substation handover · inspection · witness testing · metering · energisation · critical path · submission documents · readiness checklist
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