Siemens siprotec 7SA6 User Manual page 411

Distance protection

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Processing of the

Circuit Breaker

Auxiliary Contacts

C53000-G1176-C133-1

Figure 6-113 Current flow monitoring with the plausibility currents 3· I

The position of the circuit breaker is derived from the central function control of the

device (refer also to Section 6.20.2). 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 6-114). 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 trip.

It is possible to disable the auxiliary contact criterion. If you set the parameter switch

&KN %5. &217$&7 (Figure 6-116 above) to 1R, 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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