Breaker Failure Relays are three-phase, solid state relays designed to provide protection and
security for the power system against failure of the monitored breaker.
Breaker failure relaying is the use of a current monitoring relay to determine whether or not current
continues to flow into a faulted circuit some time after a circuit breaker has been instructed to interrupt the
circuit. In the event that current continues to flow into the faulted circuit (after a defined period of time has
elapsed sufficient for the breaker to have interrupted the current), then the circuit breaker is considered to
have failed, and steps must be initiated to trip the next set of breakers up stream in the power system.
The back up scheme must be designed to isolate both the faulted circuit and the failed breaker.
Following are several reasons why a breaker fails to clear a fault:
