2 CIRCUIT BREAKER FAIL PROTECTION
When a fault occurs, one or more protection devices will operate and issue a trip command to the relevant circuit
breakers. Operation of the circuit breaker is essential to isolate the fault and prevent, or at least limit, damage to
the power system. For transmission and sub-transmission systems, slow fault clearance can also threaten system
stability.
For these reasons, it is common practice to install Circuit Breaker Failure protection (CBF). CBF protection monitors
the circuit breaker and establishes whether it has opened within a reasonable time. If the fault current has not
been interrupted following a set time delay from circuit breaker trip initiation, the CBF protection will operate,
whereby the upstream circuit breakers are back-tripped to ensure that the fault is isolated.
CBF operation can also reset all start output contacts, ensuring that any blocks asserted on upstream protection
are removed.
Chapter 12 - CB Fail Protection P446SV
348 P446SV-TM-EN-1
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