Application - ABB RELION REC615 Technical Manual

1MRS758755 C
Figure 241: Backup trip logic
5.2.5

Application

The n-1 criterion is often used in the design of a fault clearance system. This means
that the fault is cleared even if some component in the fault clearance system is
faulty. A circuit breaker is a necessary component in the fault clearance system. For
practical and economical reasons, it is not feasible to duplicate the circuit breaker
for the protected component, but breaker failure protection is used instead.
The breaker failure function issues a backup trip command to up-stream circuit
breakers in case the original circuit breaker fails to trip for the protected
component. The detection of a failure to break the current through the breaker
is made by measuring the current or by detecting the remaining trip signal
(unconditional).
CCBRBRF can also retrip. This means that a second trip signal is sent to the
protected circuit breaker. The retrip function is used to increase the operational
reliability of the breaker. The function can also be used to avoid backup tripping
of several breakers in case mistakes occur during protection relay maintenance and
tests.
CCBRBRF is initiated by operating different protection functions or digital logics
inside the protection relay. It is also possible to initiate the function externally
through a binary input.
REC615 & RER615
Technical Manual
Protection related functions
487