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2 Functions
Figure 2-154
Circuit Breaker not
There may be cases when it is already obvious that the circuit breaker associated with
Operational
a feeder protection relay cannot clear a fault, e.g. when the tripping voltage or the trip-
ping energy is not available.
In such a case it is not necessary to wait for the response of the feeder circuit breaker.
If provision has been made for the detection of such a condition (e.g. control voltage
monitor or air pressure monitor), the monitor alarm signal can be fed to the binary input
„>CB faulty" of the 7SD5. On occurrence of this alarm and a trip command by the
feeder protection, a separate timer T3-BkrDefective, which is normally set to 0, is
started (Figure 2-155). Thus, the adjacent circuit breakers (bus-bar) are tripped imme-
diately in case the feeder circuit breaker is not operational.
Figure 2-155
Transfer Trip to the
The device has the facility to provide an additional intertrip signal to the circuit breaker
Remote End Circuit
at the remote line end in the event that the local feeder circuit breaker fails. For this,
Breaker
the transmission of the trip command is used.
To perform this intertrip, the desired command — usually the trip command which is
intended to trip the adjacent breakers — is assigned in the 7SD5 to the input function
for intertrip of the devices. This can be achieved by external wiring: the command
output is connected to the binary input at the opposite side „>Intertrip 3pol"
366
Two-stage breaker failure protection with phase segregated initiation
Circuit breaker not operational
7SD5 Manual
C53000-G1176-C169-1
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