Application – Standard Models

Breaker Failure

BE1-BPR relays are intended to provide a preprogrammed solution for most

breaker failure relaying applications. Breaker failure relaying is the use of a

current monitoring relay to determine whether or not current continues to

flow into a faulted circuit after a breaker has been instructed to interrupt the

circuit. If 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), the circuit breaker is considered to have failed. Steps must then be

taken to trip the next set of breakers in the power system to prevent system

damage. Breaker failure schemes must be designed to isolate both the faulted

circuit and the failed breaker.

Several reasons why a breaker fails to clear a fault are:

• Trip circuit is open (broken wire, blown fuse, open trip coil).

• Interrupting mechanism stuck, leaving a single phase of a three-phase circuit

connected.

• Interrupter flash-over due to the loss of dielectric strength through

contamination or damage.

• Operating mechanism failed to operate.