A BF function is initiated by all relays tripping the breaker,
and as a backup function, it preferably uses a separate CT and
ac wiring. Upon detecting a failure to interrupt, the BF
function trips all breakers that connect sources of the fault
current. This breaker failure trip (BFT) command is often
distributed via a lockout relay to prevent accidental (automatic
or manual) reclosing on the fault via the failed breaker