Application - ABB RELION REX640 Technical Manual

1MRS759142 C
5.2.6
REX640
Technical Manual
BLOCK
CB_FAULT_AL
From Timer 3
Enable timer
From Start logic
Timer 2 elapsed
From Timer 2
2 or 3 ph
I >
1, 2 or 3 ph
From level detector 1
I >
0
From level detector 2
CB failure mode "Current"
CB failure mode "Both(OR)"
CB failure mode "Both(AND)"
POSCLOSE
CB failure mode "Breaker
status"
CB failure mode "Both(OR)"
GUID-61CE4D07-7617-4FD2-97CB-57D88CEE19F6 V1 EN
Figure 577: 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.
Protection related functions
AND
OR
OR
AND
AND
CB failure trip mode
"2 out of 4"
AND
CB failure trip mode
"1 out of 3"
OR
AND
CB failure trip mode
"1 out of 4"
OR
OR
Section 5
TRBU
AND
AND
OR
AND
AND OR
AND
1075