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Functions
2.22 Circuit Breaker Failure Protection
Single-stage circuit breaker failure protection
With single-stage operation, the adjacent circuit breakers (i.e. the circuit breakers of the busbar zone and, if
applicable, the circuit breaker at the remote end) are tripped after a delay time T2 (address 3906) should the
fault not have been cleared within this time.
The timers T1-1pole (address 3904) and T1-3pole (address 3905) are then set to ∞ since they are not
needed.
You can also use the first stage alone if you wish to use different delay times after 1-pole and 3-pole tripping of
the feeder protection. In this case set T1-1pole (address 3904) and T1-3pole (address 3905) separately,
but address 3903 1p-RETRIP (T1) to NO to avoid a 1-pole trip command to the busbar. Set T2 (address
3906) to ∞ or equal to T1-3pole (address 3905). Be sure that the correct trip commands are assigned to the
desired trip relay(s).
The delay time is determined from the maximum operating time of the feeder circuit breaker, 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. The time sequence is illustrated in Figure 2-200. The dropout time for sinusoidal currents
is ≤ 15 ms. If current transformer saturation is anticipated, the time should be set to 25 ms.
Figure 2-200
Circuit breaker not operational
These delays are not necessary if the control circuit of the local circuit breaker is faulted (e.g. control voltage
failure or air pressure failure) since it is apparent that the circuit breaker is not capable of clearning the fault. If
the relay is informed about this disturbance (via the binary input „>CB faulty"), the adjacent circuit breakers
(busbar and remote end if applicable) are tripped after the time T3-BkrDefective (address 3907) which is
usually set to 0.
Address 3908 Trip BkrDefect. determines to which output the trip command is routed in the event that the
circuit breaker is not operational when a feeder protection trip occurs. Select that output which is used to trip
the adjacent circuit breakers (bus-bar trip).
410
Time sequence example for normal clearance of a fault, and with circuit breaker failure, using
single-stage breaker failure protection
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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