What is Breaker Failure Protection?
The breaker failure protection system is backup system. Specifically, this protection is depended on to take suitable action to clear a fault if, for any reason, the breaker usually anticipated to clear the fault does not.
Why breaker failure protection is needed? How it works?
A usual circuit breaker is commanded to open and close by protection and control systems that monitor conditions on the power system.
Protective relay devices detect unusual circumstances, particularly system failures (brief circuits), and direct one or more circuit breakers to be opened to isolate the failed circuit or machinery.
Protection schemes are coordinated to open the circuit breaker(s) closest to the fault to interrupt or clear the fault with minimal effect on the rest of the energy scheme. This crucial operation
How does a breaker failure protection work?
The below figure shows a failure protection system:
In this example, Breaker 3 fails to interrupt the fault current. Therefore, all sources that continue to supply fault current through Breaker 3 must be interrupted. Assuming sources at stations A and C, locally, breakers 2, 5, and 7 must be opened, or remotely, breakers 1, 6, and 8 must be opened
To implement Breaker 3 remote breaker failure backup security, the breaker 1, 6 and 8 protective relays must have overreaching components that detect faults anywhere on the line between breaker 3 and 4 and work after a time limit, typically about 0.5 seconds.
This time delay is required to allow time for operation of the local line protection on breaker 3 and for the breaker to successfully clear the fault, recognizing that time delayed tripping to coordinate with other protective relays may be included in the local protective relay scheme on breaker 3.