Digital Distance Relay with Improved Characteristics Against Distorted Transient Waveforms

Abstract

A microprocessor-based digital distance relay with improved performance in relation to low-frequency transient oscillation is introduced. New calculation algorithms for the distance element and directional element are discussed. This distance element delivers high measurement performance with an error of less than +or-3% against distorted transient waveforms containing low-frequency spectral components using a modified differential approximation algorithm based on a differential equation. The directional element utilizes a pseudo-vector product that is not affected by distortion waves for reliable direction judgement. >