High voltage isolation switch operation display circuit

As we all know, the high-voltage isolation switch is not allowed to be switched on with load, otherwise arc light will be generated, causing a short
circuit accident between high-voltage busbars and endangering equipment and personal safety. Therefore, high-voltage switchgear adopts mechanical or electrical interlocking devices. Only when
the high-voltage circuit breaker is opened, the isolating switch can be disconnected; when the circuit breaker is in the closed position, the isolating switch must not be closed. The order of operations
cannot be reversed. In order to further avoid misoperation accidents, you can also make your own high-voltage isolation switch operation display.
The principle circuit is shown in Figure 13-114.
    In the picture, QF is the normally open auxiliary contact of the high-voltage circuit breaker ; RL is the photoresistor, installed in the operating handle of the isolation switch;
H is the indicator light, with the words "Illegal operation, strictly prohibited" written on its outer cover, installed on the door cabinet .