ABB RELION 620 Series Technical Manual page 820

Section 5
Protection related functions
5.2.5
814
GUID-30BB8C04-689A-4FA5-85C4-1DF5E3ECE179 V4 EN
Figure 416: Backup trip logic
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.
1MRS757644 F
620 series
Technical Manual