Siemens Siprotec 7VK61 Manual page 119

Phase-segregated initiation
Phase segregated initiation of the breaker failure protection is necessary if the circuit breaker poles are oper-
ated 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 recom-
mended, 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 rec-
ommended to connect also for example the general device pickup to binary input „>BF release". Figure 2-
33 shows this connection.
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 „>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 2-34.
Figure 2-33
Figure 2-34
The start condition logic for the delay time(s) is basically designed as in the common phase initiation, the dif-
ference is that this logic is designed separately for each phase (Figure 2-35). 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.
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009
Breaker failure protection with phase segregated initiation — example for initiation by an exter-
nal protection device with release by a fault detection signal
Breaker failure protection with phase segregated initiation — example for initiation by an exter-
nal protection device with release by a separate set of trip contacts
2.6 Circuit breaker failure protection (optional)
Functions
119