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Functions
2.6 Circuit breaker failure protection (optional)
Figure 2-29
Current flow monitoring with plausibility currents 3·I
Monitoring the circuit breaker auxiliary contacts
It is the central function control of the device that informs the breaker failure protection on the position of the
circuit breaker (refer also to Section 2.8.1). The evaluation of the breaker auxiliary contacts is carried out in the
breaker failure protection function only when the current flow monitoring has not picked up. Once the current
flow criterion has picked up during the trip signal from the feeder protection, the circuit breaker is assumed to
be open as soon as the current disappears, even if the associated auxiliary contact does not (yet) indicate that
the circuit breaker has opened (Figure 2-30). This gives preference to the more reliable current criterion and
avoids overfunctioning due to a defect e.g. in the auxiliary contact mechanism or circuit. This interlock feature
is provided for each individual phase as well as for three-pole tripping.
It is possible to disable the auxiliary contact criterion. If you set the parameter switch Chk BRK CONTACT
(Figure 2-32 top) to NO, the breaker failure protection can only be started when current flow is detected. The
position of the auxiliary contacts is then not evaluated even if the auxiliary contacts are connected to the device.
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and 3·I
0
2
C53000-G1176-C159-3, Release date 05.2009
SIPROTEC, 7VK61, Manual
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