What is a switching program?
A switching program (or switching schedule) is a written, numbered list of every operation needed to make equipment safe for work and to restore it afterwards. It names each switch, its location, the operation and the person doing it. It is prepared and checked in advance, then each step is carried out and confirmed with the control room. Following it exactly is what stops people being hurt by live equipment.
The safe isolation sequence
- Plan the outage: notify affected customers and transfer load using the normally open point where possible.
- Isolate: open every switch that could make the equipment live, including LV back-feeds from generators or other transformers.
- Secure the isolation: lock the switches open and fit danger tags.
- Prove dead: test the voltage indicator, check the circuit is dead, and test the indicator again.
- Earth: apply earths at every point of isolation, so the work area is between earths.
- Lock and tag the earths, then issue the permit to work listing all isolation and earthing points.
Restoration runs in reverse: the permit is cancelled, earths are removed, and then the equipment is re-energised.
PractitionerClosing the normally open point parallels two feeders for a short time. Before closing it, check both feeders come from the same source busbar or are in phase, and that the loads and protection can take the ring being closed.
Regional notes
GCC
Utilities run their own safety rules with authorised persons, control room permission for every operation, and their own permit forms. Contractors work under the utility's permits for utility-owned equipment.
Australia
Network operators follow their own safety rules based on national guidelines such as ENA NENS 04, with access authorities and recipient training.
New Zealand
The EEA Safety Manual: Electricity Industry (SM-EI) sets the common framework for switching, isolation and work permits.
Asia
Utilities such as TNB and SP Group apply their own safety rules and licensing for switching operators.