Accurate superimposed component estimation for improved relay performance during power swing

There is continuous variation in amplitude, phase, and frequency of voltage and current signals during power swing in a power system. Such variation makes the memorized prefault data less accurate to be used as nonfault component while computing superimposed quantity for protection decisions during power swing. In this article, the voltage and current signal characteristics during power swing are analyzed and a technique is proposed to obtain correct nonfault components for superimposed quantity computation. The accuracy of the method in estimating the nonfault components is observed for different power swing conditions simulated in a 39-bus New England system and field data. The relay performance improvement as observed is also provided while applying the method to directional relaying, fault type classification, and fault location applications for faults during power swing. Comparative assessment reveals the superiority of the proposed method in improving the accuracy of the superimposed components computed during power swing.