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Separate delay times can be set
• for 1- or 3-pole trip repetition to the local feeder circuit breaker after a 1-pole trip of the feeder protection T1-
1pole at address 3904,
• for 3-pole trip repetition to the local feeder circuit breaker after 3-pole trip of the feeder protection T1-3pole
(address 3905),
• for trip of the adjacent circuit breakers (busbar zone and remote end if applicable) T2 at address 3906.
Note
In case of a multi-pole tripping of the feeder protection, T1-1pole and T1-3pole are started simultaneously.
By means of T1-3pole, the tripping of the circuit breaker failure protection can be accelerated in comparison
to T1-1pole. For this reason, set T1-1pole to equal or longer than T1-3pole.
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 circuit breaker failure protection, plus a safety margin which allows for any
tolerance of the delay timers. Figure 2-199 illustrates the timing of a typical circuit breaker failure scenario. The
dropout time for sinusoidal currents is ≤ 15 ms. If current transformer saturation is anticipated, the time should
be set to 25 ms.
Note
If the circuit breaker failure protection shall perform a 1-pole TRIP repetition, the time set at the AR, address
3408 T-Start MONITOR, must be longer than the time parameterized for address 3903 1p-RETRIP (T1)
to prevent a 3-pole coupling by the AR before expiry of T1.
In order to prevent an AR after „BF T2-TRIP(bus)", the time 3408 T-Start MONITOR can be set in such
a way that it expires simultaneously with T2 .
Figure 2-199
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
Time sequence example for normal clearance of a fault, and with circuit breaker failure, using
two-stage breaker failure protection
Functions
2.22 Circuit Breaker Failure Protection
409
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