Theory Of Operation - ABB REC 561 User Manual

ABB Network Partner AB
Version 1.0-00

2 Theory of operation

Breaker-failure protection
The breaker-failure protection starts on a single-phase or three-phase con-
dition, either from an external protection, or internally from a protection
trip signal in the terminal.
The breaker receiving the original protection trip command can be
retripped from the BFP. The retrip can be controlled by a current check, or
carried out as a direct retrip without any current check. The direct retrip
can be used without inconvenience, because the breaker-to-trip has
already received a tripping command, and the direct retrip does not cause
any unselective tripping
The use of retrip limits the extent of unwanted power disconnection in
case of an accidental start of the BFP at work in the initiating circuitry,
with the primary circuit in service and the load above the set current level.
The back-up trip is sent to the adjacent circuit breaker to clear the fault
and disconnect the failing circuit breaker.
IL1
START L1
t
L1
RET0: No retrip
RET1: Retrip with current check RET1:
RET2: Unconditional retrip
Fig. 3
ASD
RMS
t
t2
t
&
t1
t
t1
Logic diagram of breaker-failure protection, phase L1
1MRK 580 171-XEN
Page
BUTL1
&
RTL1
RET1
RET0
RET2
5 - 85
(X80171-3)