Use of shunt trip for earth fault protection
Use of shunt trip for earth fault protection
(OP)
I have come across many earth fault protection arrangements, where the shunt trip of the MCCB along with an earth fault relay is used to isolate a circuit with earth fault. This arrangement is not fail safe for the following,
1) Power supply for the micro relay / earth fault / shunt trip is obatained through a fuse. Opening of the fuse will will not be noticeable, but earth fault protection is out of operation.
2) Failure of the shunt trip will also lead to the same situation.
Is there a better way of interfacing the earth fault relay for fail safe operation?
1) Power supply for the micro relay / earth fault / shunt trip is obatained through a fuse. Opening of the fuse will will not be noticeable, but earth fault protection is out of operation.
2) Failure of the shunt trip will also lead to the same situation.
Is there a better way of interfacing the earth fault relay for fail safe operation?






RE: Use of shunt trip for earth fault protection
To answer your question, you can provide a more reliable power source for the shut trip and relay. Such as a battery back up, etc.
Any component can fail any time, but that is why regular testing is recommended.
You can also use the MCCB with electronic trip units with built-in EF function in it.
Just remember that EFP is not required by Code for all circuits, but if you application dictates it, its fine. EF protection can also be source of nuisance trips or miscoordination.
RE: Use of shunt trip for earth fault protection
RE: Use of shunt trip for earth fault protection
RE: Use of shunt trip for earth fault protection
In the US, energize-to-trip is by far the most common approach, even for critical applications. For improved reliability, dual battery systems, dual trip coils, dual relays etc are often used, in conjunction with some type of breaker failure logic.
RE: Use of shunt trip for earth fault protection
RE: Use of shunt trip for earth fault protection