Application :- After Cl;osing or continuous supervision of the trip circuit or circuit breaker.
1.Failure of Trip Supply
2.Open Circuit of trip Coil or trip circuit wiring
3.Failure of mechanism to complete the tripping operation.
A CTZM Relay is used at ACB in PCC which feeds the MCC and the delay settins are provided there at.
When 10 MVA primary side SF6 primary side SF6 breaker operates, there should be an interlock to open the breaker on secondary side ( to prevent closing on load T/F) but this is not provided and is done manually.
CBCT :- Core Balance Current Transformer, Used for Unbalanced Current Protection.