The isolating switch control wiring and the corresponding circuit breaker are locked, which can effectively prevent the pull and combine isolation switch with load. However, in the operation of the bus-side disconnecting switch and the line-side disconnecting switch, due to human factors, the operation sequence may be reversed. This is not allowed by the switch and the operation principle of the switch, and is also one of the causes of the accident in the power system. In order to prevent the isolation switch operation sequence from being reversed, the plant and station that have not used the program lock to prevent mistakes will be improved by the original isolating switch control wiring, which can prevent misoperation and reduce unnecessary accidents.

1.Isolation switch control locking circuit improvement principle

In the isolation switch control and lockout circuit, the auxiliary contact of the isolation switch is serially connected, that is, the bus side isolation switch controls the normally closed auxiliary contact of the line isolation switch in the latching loop, and the line side isolation switch control loop is connected to the bus side isolation switch. Open the auxiliary contacts.

2. Use the electromagnetic lock to prevent the error of isolation and open and close the lock wire (take single bus line as an example). Figure 1 shows the original control wiring. This type of wiring can effectively prevent pull-out and disconnect switches with load, but it may cause the order of operation of the disconnect switch to be reversed.

Figure 2 Improved Single Bus Feeder Isolation and Closure

See Figure 2 for improved wiring. Power failure operation: After the circuit breaker is opened, the line side isolation switch can only be opened first to open the bus side isolation switch.

Power transmission operation: In the open position of the circuit breaker, only the busbar side isolation barrier can be closed before the line side isolation barrier can be closed. This type of wiring not only prevents the load from pulling and closing the isolation switch, but also prevents the violation of the operating principles of the switch and the switch. 3. Improve the advantages of wiring

(1) The improved wiring not only retains the advantages of the original isolating switch control wiring, the most important is that it can effectively prevent the violation of the operating principle of the switch, knife gate operation, and reduce unnecessary accidents.

(2) This improved wiring is simple, reliable, and less investment. Applicable to the use of electromagnetic lock anti-misuse wiring and pneumatic control, electric operation, electro-hydraulic operation of the isolation switch control wiring.

(3) In a device that does not use a program lock to prevent mistakes, it is equivalent to a program lock.