P44x/EN AP/Hb
MiCOM P40 Agile P442, P444
(AP) 5-
Figure 45: Weak infeed phase selection logic
DDB: ‘DIST. UNB CR’ (or ‘DEF. UNB CR’) is used as a filter to avoid a permanent phase
selection which could be maintained if CBaux signals are not mapped in the PSL (when line
is opened).
The additional weak infeed trip logic is:
Weak infeed trip: No Distance Zone Operation, plus reverse directional decision, plus
V<, plus Channel Received.
Weak infeed tripping is time delayed according to the ‘WI: Trip time delay’ value, usually set
to 60 ms. Due to the use of phase segregated undervoltage elements, single pole tripping
can be enabled for WI trips (DDB: ’WI Trip A’, ‘WI Trip B’ or ‘WI Trip C’) if required. If single
pole tripping is disabled a three pole trip will result after the time delay.
Figure 46: Weak infeed trip decision logic
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