Siemens SIPROTEC 4 7VK61 Manual page 126

Functions
2.6 Circuit breaker failure protection (optional)
If the circuit breaker failure protection is configured with zero sequence current threshold (address 139 =
vorh. mit 3I0>), the pickup threshold for the zero sequence current 3I0> BF (address 3912) can be set
independently of I> BF.
Normally, the circuit breaker failure protection evaluates the current flow criterion as well as the position of
the circuit breaker auxiliary contact(s). If the auxiliary contact(s) status is not available in the device, this crite-
rion cannot be processed. In this case, set address 3909 Chk BRK CONTACT to NO.
Two-stage circuit breaker failure protection
With two-stage operation, the trip command is repeated after a time delay T1 to the local feeder circuit
breaker, normally to a different set of trip coils of this circuit breaker. A choice can be made whether this trip
repetition shall be 1-pole or 3-pole if the initial feeder protection trip was 1-pole (provided that 1-pole trip is
possible). This choice is made in address 3903 1p-RETRIP (T1). Set this parameter to YES if the first stage
is to trip 1-pole, otherwise set it to NO.
If the circuit breaker does not respond to this trip repetition, the adjacent circuit breakers are tripped after T2,
i.e. the circuit breakers of the busbar or of the concerned busbar section and, if necessary, also the circuit
breaker at the remote end unless the fault has been cleared.
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
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In case of multi-phase tripping of the feeder protection, T1-1pole and T1-3pole are started in parallel.
T1-3pole therefore allows accelerating the tripping of the breaker failure protection compared to
T1-1pole. Therefore, you should set T1-1pole equal to 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.
dropout time for sinusoidal currents is ≤ 15 ms. If current transformer saturation is anticipated, the time
should be set to 25 ms.
NOTE
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If the breaker failure protection is to perform a single-pole TRIP repetition, the time set for the AR,
address3408 T-Start MONITOR, has to be longer than the time set for address 3903 1p-RETRIP (T1)
to prevent 3-pole coupling by the AR before T1 expires.
To prevent AR after
with T2.
126
Figure 2-47 illustrates the timing of a typical circuit breaker failure scenario. The
BF T2-TRIP(bus) , the time 3408T-Start MONITOR can be set to expire together
SIPROTEC 4, 7VK61, Manual
C53000-G1176-C159-5, Edition 05.2018