A novel negative sequence reactance based high speed directional relay algorithm

摘要

Negative sequence (NS) directional protection may not provide desirable results when the fault component magnitude is quite small as a result of the existence of high resistance faults or remote forward faults with a strong source. Full cycle (FC) Fourier-based algorithms are widely used in digital relaying devices in order to estimate phasors. The common required time for fault detection in these relays is approximately one power frequency cycle. This paper presents a novel NS reactance-based high speed directional relay algorithm. General park transformation (GPT) is applied to calculate NS components within two to three sample intervals, which greatly increases the protection’s operation speed. The fast response is comparable to transient component-based protection but with improved reliability. The NS reactance-based directional elements provide high sensitivity with no need to set the voltage or current threshold. The principle can correctly detect the fault direction even in the presence of low voltage and current. Extensive simulation results verified the effectiveness of the proposed algorithm and show that it has adequate selectivity, sensitivity and reliability, a fast operating response and immunity to fault resistance under a variety of system and unbalanced fault conditions. These excellent properties make it a good prospect for engineering applications. Copyright © 2014 John Wiley & Sons, Ltd.