A New Digital Distance Relaying Scheme for Compensation of High-Resistance Faults on Transmission Line

Performance of the conventional ground distance relaying scheme is adversely affected by different types of ground faults, such as single line to ground, double line to ground, and simultaneous open conductor and ground. This effect is more pronounced due to the considerable value of fault resistance and direction and magnitude of power flow. The work presented in this paper addresses the aforementioned problems encountered by the conventional ground distance relaying scheme when protecting doubly fed transmission lines. Further, a new digital distance relaying scheme is proposed which compensates the errors produced by the conventional ground distance relaying scheme using local-end data only. The detailed analysis of the apparent impedance as seen from the relaying point by the conventional ground distance relaying scheme and the proposed scheme during different types of ground faults is also presented in this paper. The feasibility of the proposed scheme has been tested using MATLAB/SIMULINK software. The simulation results demonstrate the effectiveness of the proposed scheme since it provides accuracy on the order of 98%.

I. Introduction

Digital distance relays, used to protect extremely high voltage (EHV) and ultra-high voltage (UHV) transmission lines, can realize some very useful functions which were not possible with previous generation relays, such as long-term storage of prefault data, multiple setting groups, programmable logic, adaptive logic, and sequence-of-events recording [1], [2]. However, these relays do not have successful solutions to the cumbersome problems, such as the presence of high fault path resistance during different types of ground faults and remote infeed [3]. Under these conditions, part of the fault resistance is translated into inductance or capacitance, causing over-reach or under-reach of the distance relay [4], [5].