Siemens siprotec 7SA6 User Manual page 414

Functions
Phase Segregated
Initiation
6-232
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 initiation of the breaker failure protection must also be possible by further external
protection devices, it is recommended, for security reasons, to connect an additional
release signal (e.g. fault detection, pickup) at the input "!%) UHOHDVH", besides the
trip commands at the inputs "!%) 6WDUW /", "!%) 6WDUW /", and "!%) 6WDUW
/". Figure 6-117 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 ´!%)
UHOHDVH" 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
6-118.
The starting condition logic for the delay times is shown in Figure 6-119. 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.
external
prot. device
L+
Figure 6-117 Breaker failure protection with phase segregated initiation — example for
initiation by an external protection device with release by a fault detection signal
Trip L1
Trip L2
Trip L3
Pick-up
7SA6
>BF Start L1
>BF Start L2
>BF Start L3
>BF release
C53000-G1176-C133-1
L–
7SA6 Manual