Functions
2.22 Circuit Breaker Failure Protection
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
401
Phase-segregated initiation
Phase segregated initiation of the circuit breaker failure protection is necessary if the circuit breaker poles are
operated individually, e.g. if 1-pole automatic reclosure is used. This is possible if the device is able to trip 1-
pole.
If the circuit breaker failure protection is intended to be initiated by further external protection devices, it is rec-
ommended, for security reasons, to connect two binary inputs to the device. Besides the three trip commands
of the external relay to the binary input „>BF Start L1“, „>BF Start L2“ and „>BF Start L3“ it is
recommended to connect also, for example, the general device pickup to binary input „>BF release“. Figure
2-189 shows this connection.
Nevertheless, it is possible to initiate the circuit breaker failure protection in single-channel mode should a sep-
arate release criterion not be available. The binary input „>BF release“ must then not be assigned to any
physical input of the device during configuration.
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 separate set of trip contacts can produce such a release
signal as shown in Figure 2-190.
Figure 2-189 Breaker failure protection with phase segregated initiation — example for initiation by an
external protection device with release by a fault detection signal
Figure 2-190 Breaker failure protection with phase segregated initiation — example for initiation by an
external protection device with release by a separate set of trip contacts
In principle, the starting condition logic for the delay time(s) is designed similar to that for the common phase
initiation, however, individually for each of the three phases (as shown in Figure 2-191). Thus, current and ini-
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