A New Half-Cycle Adaptive Phasor Estimator Immune to the Decaying

The paper presents a new half-cycle adaptive phasor estimation algorithm for digital protective relaying. The algorithm is immune to an exponentially decaying dc component regardless of its initial magnitude and time constant. The algorithm is intended for current signals and improves both the magnitude and impedance measurements. The new measuring technique is based on the recursive half-cycle Fourier filter with a separate adaptive function allowing for thorough rejection of an aperiodic signal component. Analysis of the algorithm’s performance, both analytical and by simulation, is included. The presented algorithm outperforms the classical mimic filtering broadly used in today's relays.