Toshiba GR-200-5 Instruction Manual page 154

6F2T0207 (0.01)
Circuit breaker fail protection (CBF)
When a circuit breaker (CB) fails to remove a fault because of the CB failing to open, the
function of circuit breaker fail protection (CBF) is to remove the fault by the back-tripping of
other CBs. For example, if a fault current continues to flow following the issue of a trip
command, the CBF function determines that the CB failure has occurred; the CBF function
will issue another trip command to the adjacent CB(s) and/or the upstream CB.
Although a trip command will have been issued by other protection functions, the CBF
protection has own relay elements and own timers that are used to detect the continuing
presence of a fault following the issuance of the trip command. The relay elements are termed
OCCBF and EFCBF, which run as protection functions within CBF.
GRE200 (5,6)
- 134 -