Siemens SIPROTEC 7SD610 Manual page 188

Functions
2.13 Circuit Breaker Failure Protection
started (Figure 2-76). Thus, the adjacent circuit breakers (bus-bar) are tripped immediately in case the feeder
circuit breaker is not operational.
Figure 2-76
Transfer trip to the remote end circuit breaker
When the local feeder circuit breaker fails, tripping of the circuit breaker at the remote line end is often also
desired. This requires the command to be transmitted.
In case of 7SD610 the corresponding command — usually the trip command which is intended to trip the ad-
jacent breakers — is assigned to the input function for intertrip of the devices. This can be achieved by external
wiring: The command output is connected to the binary input „>Intertrip 3pol" (No. 3504) (see also
Section 2.4). An easier procedure is to combine the command output with the intertrip input via the user defin-
able logic functions (CFC).
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.
This situation is shown in Figure 2-77. The fault is located — as seen from the current transformers (= mea-
surement location) — on the bus-bar side, thus, it will not be regarded by the feeder protection device as a
feeder fault. It can only be detected by the bus-bar 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 circuit breaker of the feeder has properly responded to the trip command.
Figure 2-77
The end fault protection has the task to recognize this situation and to transmit a trip signal to the remote end
of the line to clear the fault. For this purpose, the output command „BF EndFlt TRIP" (No. 1495) is available
to trigger the intertrip input of the differential protection — if applicable, together with other commands for trip-
ping at the remote end. This can be achieved by external wiring or via CFC.
188
Circuit breaker not operational
End fault between circuit breaker and current transformers
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011