2.13 Circuit Breaker Failure Protection
185
7SD610 Manual
C53000-G1176-C145-4
the application of the feeder protection, common phase or phase-segregated initiation
conditions may occur. The tripping by the breaker failure protection is always three-
pole.
The simplest solution is to start the delay timer T2 (Figure 2-70). The phase-segregat-
ed initiation signals are omitted if the feeder protection always trips three-pole or if the
circuit breaker is not capable of single-pole tripping.
If different delay times are to be achieved after a single-pole trip or three-pole trip, the
delay times T1-1pole and T1-3pole are used according to Figure 2-71.
Figure 2-70 Single-stage breaker failure protection with common phase initiation
Figure 2-71 Single-stage breaker failure protection with different delay times
With two-stage breaker failure protection the trip command of the feeder protection is
usually repeated, after a first time stage, to the feeder circuit breaker, often via a
second trip coil or set of trip coils, if the breaker has not responded to the original trip
command. A second time stage monitors the response to this repeated trip command
and trips the breakers of the relevant busbar section if the fault has not yet been
cleared after this second time.
For the first stage a different delay T1-1pole can be set for single-pole trip than for
three-pole trip by the feeder protection. In addition, you can use this setting (parameter
1p-RETRIP (T1)) to define whether this repeated trip should be single-pole or three-
pole.
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