ABB RELION REF615R, Technical Manual

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POSCLOSE
Enable timer
From Start logic
CB failure mode ”Current”
CB failure mode ”Breaker
status”
CB failure mode ”Both”
AND
CB failure trip mode
”1 out of 3"
CB failure trip mode
”1 out of 4"
AND
AND
AND
CB failure trip mode
”2 out of 4"
OR
OR
AND
51P
From level detector 1
TRBU
51N/G
From level detector 2
AND
OR
OR
OR
CB failure mode ”Both”
AND
AND
BLOCK
Timer 2 elapsed
From Timer 2
CB_FAULT_AL
From Timer 3
AND
OR
GUID-30BB8C04-689A-4FA5-85C4-1DF5E3ECE179-ANSI V1 EN
Figure 159: 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).
50BF 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.
1MRS240050-IB C
Section 5
Protection-related functions
REF615R 325
Technical Manual