2.18 Circuit breaker failure protection (optional)
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7SA522 Manual
C53000-G1176-C155-3
start signal is maintained until the auxiliary contact criterion reports that the circuit
breaker is open.
Initiation can be blocked via the binary input ´!%/2&.%NU)DLOµ (e.g. during test of
the feeder protection relay). Additionally, an internal blocking option is provided.
Figure 2-125 Breaker failure protection with common phase initiation
Phase Segregated
Initiation
Phase segregated initiation of the breaker failure protection is necessary if the circuit
breaker poles can be operated individually, e.g. if single-pole automatic reclosure is
used. This is possible if the device is able to trip single-pole.
If the breaker failure protection is intended to be initiated by further external protection
devices, it is recommended, for security reasons, to connect two starting criteria to the
device. Besides the three trip commands of the external relay to the binary input ´!%)
6WDUW/µ, ´!%)6WDUW/µ and ´!%)6WDUW/µ it is recommended to connect
also for example the general device pickup to binary input ´!%)UHOHDVHµ. Figure
2-126 shows the connections of this dual-channel initiation.
Nevertheless, it is possible to initiate the breaker failure protection in single-channel
mode should a separate release criterion not be available. The binary input ´!%)
UHOHDVHµ must then not be assigned to any physical input of the device during con-
figuration.
If the external protection device does not provide a general fault detection signal, a
general trip signal can be used instead. Alternatively, the parallel connection of a sep-
arate set of trip contacts can produce such a release signal as shown in Figure 2-127.
The starting condition logic for the delay times is shown in Figure 2-128. In principle,
it is designed similar to that for the common phase initiation, but individually for each
of the three phases. Thus, current flow and initiation conditions are processed for each
phase. In case of single-pole interruption before an automatic reclose cycle, current
disappearance is reliably monitored for the tripped breaker pole only.
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