1 Used to mount circuit breaker, transformer and other components in the withdrawable switchgear, as auxiliary operation of components with busbar. When operation with internal mechanism of circuit breaker and other interlock mechanism of mid-placed cabinet, it can satisfy the interlock requirement of "5 preventions" stipulated in GB3906.

2 Only when the handcart is under testing/isolating or working position, the circuit breaker can make. After that, the handcart is under locked state, which avoids false connecting or making of the spacing contact.

3 When the handcart is under working position or away from testing/isolating position for 10mm, the earthing switch fails to make,avoided powered false making of the switch.

4 When the earthing switch makes, the handcart shall not shift from testing/isolating to working position, avoiding the switch closing the circuit breaker in making.

5 When the chassis enters cabinet, once away from testing/isolating position, the handcart fails to draw out from the cabinet.