A Novel Phaselet Based Fast Distance Relay

This paper describes a new algorithm of fast distance relay based on the conception of phaselets. The principle is proposed by means of directly comparing phase difference between the operating voltage phaselet and the polarizing phaselet on the basis of new phaselet equation of transmission line and new definition of operating voltage. Additionally, the exponential decaying DC component matches the new phaselet equation as well as the power component does. The new algorithm, therefore, needs neither converting the phaselets into phasors, nor removing the decaying DC offsets. The digital algorithms of fast MHO relay and fast zero-sequence reactance relay are also presented in detail. The EMTP simulation tests associated with a simple transmission system and 500 kV transmission system in Shan Dong power system show that the new algorithms have the properties of high speed with simple calculation, and are not influenced by DC decaying component as well as the high frequency components are effectively restrained