High Voltage Switching Program Procedure

Purpose. This procedure describes how high voltage switching programs are developed, validated, directed and recorded so that apparatus is isolated and restored in the correct sequence.

1.Developing the program

A switching program will be written by an authorised switching program writer using the current network diagram, the work order and the access requirements. It must list every switching step in sequence, the apparatus and location, the operator, the expected network state after each step, and the earths to be applied. Programs must consider supply to customers, protection settings, load transfer and the effect on other work in progress.

2.Validating the program

Every program must be checked by a second authorised person who was not the writer, against the network diagram and the isolation and earthing requirements of the access authority. The checker signs the program in the switching program register. A program that is changed after validation must be rechecked.

3.Directing switching

The network controller directs each step to the field switching operator by radio or phone using the step number, the apparatus identification and the operation. The operator repeats the instruction back, performs the operation, confirms the result and the time, and the controller records it in the register before directing the next step. No step may be performed out of sequence.

• Direct one step at a time by step number and apparatus identification
• Operator repeats back before operating
• Confirm result and time after each step
• Record before directing the next step
• Stop and re-validate if the network state differs from the program

4.Isolation, proving and earthing

After isolation steps are complete, the operator will prove the apparatus de-energised with a tested high voltage detector proven before and after use, apply the earths in the program and confirm each earth to the controller. Isolation points will be locked with a network lock and tagged with the program number.

5.Restoration

Restoration switching will begin only after every access authority on the apparatus has been cancelled and recorded. Earths will be removed in the program sequence and confirmed before any closing operation. The controller will confirm load and protection status by supervisory control after restoration.

6.Abnormal events

If a switching operation fails, a protection operation occurs during the program or a step cannot be performed as written, the controller will stop the program, make the network safe, record the event and consult the duty manager before proceeding. The event will be entered in the incident register.