Siemens siprotec 7SA6 User Manual page 423

Circuit Breaker not
Operational
End Fault
Protection
Pole Discrepancy
Supervision
7SA6 Manual
C53000-G1176-C133-1
Fault inception
Fault clearance time normal
Prot. CB operating time Reset
trip
Initiation breaker
failure protection
Time delay T2 of breaker
failure protection
Total fault clearance time with breaker failure
Figure 6-128 Time sequence example for normal clearance of a fault, and with circuit breaker
failure, using single-stage breaker failure protection
If the circuit breaker associated with the feeder is not operational (e.g. control voltage
failure or air pressure failure), it is apparent that the local breaker cannot clear the
fault. Time delay before tripping the adjacent breakers is not necessary in this case. If
the relay is informed about this disturbance (via the binary input "!&% IDXOW\", the
adjacent circuit breakers (bus-bar and remote end if applicable) are tripped after the
time 7%NU'HIHFWLYH (address  ) which is usually set to .
Address   7ULS %NU'HIHFW determines to which output the trip command is
routed in the event that the breaker is not operational when a feeder protection trip
occurs. Select that output which is used to trip the adjacent breakers (bus-bar trip).
The end fault protection can be switched 2Q or 2II separately under address  
(QG )OW VWDJH. An end fault is a short-circuit between the circuit breaker and the
current transformer set of the feeder. The end fault protection presumes that the
device is informed about the circuit breaker position via breaker auxiliary contacts
connected to binary inputs.
If, during an end fault, the circuit breaker is tripped by a reverse fault stage of the
feeder protection or by the bus-bar protection (the fault is a bus-bar fault as
determined from the location of the current transformers), the fault current will
continue to flow, because the fault is fed from the remote end of the feeder circuit.
The time 7(QG)DXOW (address  ) is started when, during the fault detection
condition of the feeder protection, the circuit breaker auxiliary contacts indicate open
poles and, at the same time, current flow is detected (address  ). The trip
command of the end fault protection is intended for the transmission of an intertrip
signal to the remote end circuit breaker.
Thus, the delay time must be set such that it can bridge out short transient apparent
end fault conditions which may occur during switching of the breaker.
The pole discrepancy supervision can be switched 2Q or 2II separately under
address   3ROH'LVFUHSDQF\. It is only useful if the breaker poles can be
operated individually. It avoids that only one or two poles of the local breaker are open
continuously. It has to be provided that either the auxiliary contacts of each pole or the
series connection and the parallel connection of the auxiliary contacts are connected
to the device's binary inputs. If these conditions are not fulfilled, switch the pole
discrepancy supervision 2II.
Safety
I> BF margin
CB–operating time
(adjacent CBs)
Functions
6-241