Amplitude-independent comparators for UHS directional relays

When applying techniques of phase or amplitude comparison in ultra-high speed (UHS) directional relays, it turns out that in order to safely assess directionality, prior knowledge of the amplitude of the superimposed voltages and currents is required so that the proper thresholds can be set. Therefore, very fast algorithms have to be devised that would take into account anticipated values of these magnitudes in order to assure secure trips in the shortest possible time. Because of this, algorithms have to incorporate into their settings thresholds for these parameters. In this paper, an algorithm is introduced where amplitudes of superimposed quantities are automatically taken care of