By definition, BF protection is a backup function.
Therefore, it is typically biased for security rather than
dependability. A BF protection system will be called upon to
not trip many more times than it will be called upon to trip.
Because a BF operation results in tripping breakers that isolate
all the adjacent zones of the power system, typically including
the bus, the consequences of BF false operation are usually
serious. BF protection security has the same importance as bus
protection security.