fundamental value of waveform is quite low; hence, relay is
not excited especially when Grand Rapids station is in
generator mode. The magnitude of current in HV side of
transformer in effect of Ferroresonance is much higher than
LV side; hence, differential current is increased and relay
operates. N.S.D Element operates sequentially due to swing
behavior of measured sequence components and phase
difference between envelopes of parameters even in a radial
system.