2.9 Weak-infeed tripping
197
7SA522 Manual
C53000-G1176-C155-3
After a security margin time of 40 ms following the start of the receive signal, the weak-
infeed tripping is released if the remaining conditions are satisfied: undervoltage,
circuit breaker closed and no pickup of the distance protection or of the earth fault pro-
tection.
To avoid a faulty pickup of the weak infeed function following tripping of the line and
reset of the fault detection, the function cannot pick up anymore once a fault detection
in the affected phase was present (RS flip-flop in Figure 2-88).
In the case of the earth fault protection, the release signal is routed via the phase seg-
regated logic modules. Single-phase tripping is therefore also possible if both distance
protection and earth fault protection or exclusively earth fault protection issues a
release condition.
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