The second breaker failure protection is switched at address 7101 BREAKER FAILURE ON or OFF.
Initiation
Three statements are essential for the correct initiation of the circuit breaker failure protection:
The
Current-flow Monitoring ensures that the current flow stops after the trip command has been issued to
the breaker to be monitored. It uses the values set in the General Power System Data 2 is decisive (see Section
2.1.6.1 Setting Notes under margin heading “Circuit Breaker Status”). The decisive value is the setting assigned
to the side or measuring location that indicates the current of the monitored circuit breaker (addresses 1111
to 1125). This value will certainly be undershot in case of an open circuit breaker.
The assignment of the
CB auxiliary contacts or the CB feed-back information was executed in accordance with
Section 2.1.4.4 Circuit Breaker Data. The configuration of the respective binary inputs must be complete.
The tripping command for the monitored breaker is determined by address 7011 oder 7012 START WITH
REL. (depending on the version of the device). Choose the number of the output relay which shall trip the
breaker to be monitored. If START WITH REL. is parameterised to 0 , no initiation occurs via the internal
binary output. Since 7UT6x will normally trip several circuit breakers by the various protection functions, the
device must be informed about which trip command is decisive for the initiation of the breaker failure protec-
tion. If the breaker failure protection is intended to be 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 initiation of the circuit
breaker failure protection if this activation is effected simultaneously 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.
Two-stage Breaker Failure Protection
In two-stage operation, the trip command is sent after a delay time T1 (address 7015) 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 cascading 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 7016) 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 protection, plus a safety margin which allows for any toler-
ance of the delay timers. The time sequences are illustrated in Figure 2-112. For sinusoidal currents one can
assume that the reset time of the current detectors is about
1
/
2
cycle but if current transformer saturation is
expected, then 1
1
/
2
cycles should be assumed as worst case.
Functions
2.17 Circuit Breaker Failure Protection
248 SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016
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