Siemens Siprotec 7VK61 Manual page 124

Functions
2.6 Circuit breaker failure protection (optional)
started (Figure 2-39). Thus, the adjacent circuit breakers (bus-bar) are tripped immediately in case the feeder
circuit breaker is not operational.
Figure 2-39
Transfer trip to the remote end circuit breaker
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).
End fault protection
An end fault is defined here as a short–circuit which has occurred at the end of a line or protected object,
between the circuit breaker and the current transformer set.
Figure 2-40 shows the situation. The fault is located — as seen from the current transformer (= measurement
location) — on the busbar side, it will thus not be regarded as a feeder fault by the feeder protection relay. It
can only be detected by either a reverse stage of the feeder protection or by the busbar protection. However,
a trip command given to the feeder circuit breaker does not clear the fault since the opposite end continues to
feed the fault. Thus, the fault current does not stop flowing even though the feeder circuit breaker has properly
responded to the trip command.
Figure 2-40
The end fault protection has the task to recognize this status and to transmit a trip signal to the remote end(s)
of the protected object to clear the fault. For this purpose, the output command „BF EndFlt TRIP" is avail-
able to trigger a signal transmission device (e.g. power line carrier, radio wave, or optical fibre) — if applicable,
together with other commands that need to be transferred.
The end fault is recognized when the current continues flowing although the circuit breaker auxiliary contacts
indicate that the breaker is open. An additional criterion is the presence of any breaker failure protection initiate
124
Circuit breaker faulty
End fault between circuit breaker and current transformers
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009