Siemens SIPROTEC 7UT613 series Manual page 273

Two-stage Breaker
Failure Protection
Single-stage
Breaker Failure
Protection
7UT613/63x Manual
C53000-G1176-C160-2
initiated also by external trip commands (for the same breaker) the device has to be
informed about this trip via the binary input „>BrkFail extSRC" (No 047.2651).
The activation of the relay contact set under START WITH REL., only causes the ini-
tiation of the circuit breaker failure protection if this activation is effected simultaneous-
ly with the indication (fast indication) of a protection function.
If the circuit breaker is supposed to be activated behind the respective relay contact
by means of a controlled indication, this message must be conducted, for example, via
the DC (direct coupling) function and its TRIP command. During configuration, the DC-
TRIP would cause the respective relay to start the circuit breaker failure protection.
In two-stage operation, the trip command is sent after a delay time T1 (address 7115)
to the locally monitored feeder circuit breaker, normally to a separate set of trip coils
of the breaker.
The TRIP command of a circuit breaker failure protection may not be allocated to a
relay, which is monitored by a different circuit breaker failure protection. This cascad-
ing does not cause initiation.
If the circuit breaker does not respond to the repeated trip command, the protection
trips after a second delay time T2 (address 7116) the adjacent circuit breakers, i.e.
those of the busbar or the affected busbar section and, if necessary, also the circuit
breaker at the remote end, if the fault is not yet eliminated.
The delay times are set dependant on the maximum operating time of the feeder
circuit breaker and the reset time of the current detectors of the breaker failure protec-
tion, plus a safety margin which allows for any tolerance of the delay timers. The time
sequences are illustrated in Figure 2-110. For sinusoidal currents one can assume that
the reset time of the current detectors is about
uration is expected, then 1
Figure 2-110 Time sequence for normal clearance of a fault, and with circuit breaker failure
example for two-stage breaker failure protection
With single-stage operation, the adjacent circuit breakers (i.e. the breakers of the
busbar zone and, if applicable, the breaker at the remote end) are tripped after a delay
time T2 (address 7116) following initiation, should the fault not have been cleared
within this time.
2.17 Circuit Breaker Failure Protection
1
/
2
1
/ cycles should be assumed as worst case.
2
cycle but if current transformer sat-
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