High Speed Digital Directional Comparison Relaying

Abstract

A high speed directional comparison relay based on the evaluation of the locally measured deviations of the voltage and current from their prefault values is described in this paper. Signal processing techniques are used to damp out the exponentially decaying dc component and high frequency transient components so that the operation of the relay depends on the power frequency components of the voltage and current deviation signals. The direction to a fault is determined by detecting the first transgression of the fault trajectories across threshold boundaries in the deviation plane. Studies on a three phase power system model show that the direction to a fault is determined within a first few milliseconds following the inception of a fiult.

Directional Relaying of Series-compensated Line Using an Integrated Approach

“…Directional relaying algorithms use different sequence components of voltage and current. Positive-sequence components are available for all fault types but do not provide good results for high resistance fault [6][7][8][9]. A negative-sequence component based approach is not affected during a resistive fault, but such components are not available for balanced faults.…”