... necessary, fewer parts, high reliability;WIDE RANGE IN FREQUENCY TRACKING: In the 40 to 60 Hz range, FFT algorithm ... type: Over, under, window trig, ROC trig; Harmonic, single phase P,Q, 3 phases P,Q, frequency, Positive sequence voltage ... zero sequence differential relayTransformer over current relayTransformer over load relayTest: Generator open, short, synchronizing, destroy magnetic, 10% step; ...