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Figure 2-131
Two-stage breaker failure protection with phase segregated initiation
Circuit Breaker not
Operational
Transfer Trip to the
Remote End Circuit
Breaker
7SA522 Manual
C53000-G1176-C155-3
There may be cases when it is already obvious that the circuit breaker associated with
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
´!&% IDXOW\µ of the 7SA522. On occurrence of this alarm and a trip command by
the feeder protection, a separate timer 7%NU'HIHFWLYH, which is normally set to
0, is started (Figure 2-132). Thus, the adjacent circuit breakers (bus-bar) are tripped
immediately in case the feeder circuit breaker is not operational.
Figure 2-132
Circuit breaker faulty
The device has the facility to provide an additional intertrip signal to the circuit breaker
at the remote line end in the event that the local feeder circuit breaker fails. For this, a
suitable protection signal transmission link is required (e.g. via communication cable,
power line carrier transmission, radio transmission, or optical fibre transmission). With
devices using digital transmission via protection interface, the remote commands can
be applied (see also Section 2.5).
To perform this intertrip, the desired command — usually the trip command which is
intended to trip the adjacent breakers — is assigned to a binary output of the device.
The contact of this output triggers the transmission device. When using digital signal
transmission the command is connected to a remote command via the user-defined
logic (CFC).
2.18 Circuit breaker failure protection (optional)
307
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