Functions
2.13 Circuit Breaker Failure Protection
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
180
Figure 2-66 Current flow monitoring with plausibility currents 3·I
0
and 3·I
2
1) only available/visible if 139 is set to enabled w/ 3I0>
Monitoring the circuit breaker auxiliary contacts
It is the central function control of the device that informs the circuit breaker failure protection on the position of
the circuit breaker (refer also to Section 2.16.1). The evaluation of the circuit breaker auxiliary contacts is
carried out in the circuit 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 2-67). 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 3-pole tripping.
It is possible to disable the auxiliary contact criterion. If you set the parameter switch Chk BRK CONTACT
(Figure 2-69 top) to NO, the circuit 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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