8-4 F60 Feeder Protection System GE Multilin
8.1 HIGH-IMPEDANCE (HI-Z) FAULT DETECTION 8 THEORY OF OPERATION
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8.1.13 HI-Z VOLTAGE SUPERVISION ALGORITHM
This algorithm was implemented to minimize the probability of a false Hi-Z indication due to bus voltage dips (e.g. from par-
allel feeder faults). A fault on a parallel line can cause voltage dips that will produce a decrease in the line load which can
be mistaken by Hi-Z element as Loss of Load.
Every two cycle the voltage on each phase is checked against the
HI-Z V SUPV THRESHOLD. If the voltage on any phase has
dropped by a percentage greater then or equal to this setting, the Loss of Load flag will be blocked. The blocking is not
done on a per- phase basis. If one phase voltage shows a dip, the block is applied for all phases. Also the High Impedance
Oscillography will record that a voltage dip was experienced. The Oscillography record is phase specific.
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