New algorithms for microprocessor-based distance relaying

Abstract System impedance calculation for distance relaying requires extraction of fundamental frequency components from highly distorted post-fault relaying signals. Many algorithms are available for extracting the fundamental frequency component, but most of them involve a large amount of computation, whilst others have low accuracy, or poor convergence, or both. This paper describes two algorithms based on the Hartley transform. They are computationally simple, have good frequency response and give fast convergence in the calculation of resistance and reactance. Their efficacy has been examined using representative voltage and current relaying signals. The results obtained and presented here are gratifying.