Generator manufacturers usually recommend the use of breaker failure protection as
an integral part of the overall generator protection [7]. A simplified form of breaker failure
protection is shown in Figure 18.17. This scheme requires the use of fault detectors (50BF)
and timers (62BF). Separate fault detectors and times must be used for each breaker, such as
breakers 2 and 3 in Figure 18.17. The primary and backup protective systems, on detecting a
fault, will attempt to trip the circuit breakers and, at the same time, will start the breaker failure
timers (62BF2 and 62BF3). If the breaker does not clear the fault before the timer completes
its cycle, the timer will trip the other breakers that are required to isolate the fault. Thus, if
breaker 3 fails, all breakers on bus N must be tripped. If breaker 2 fails, breaker 1 and the
remote end of line A must be tripped. The line should be tripped by a transfer trip signal since
the remote end relays may not detect the internal generator fault.