Research of single-phase faults in 6–35 KV branched overhead distribution network

Abstract

The relevance of the problem discussed in the paper is stipulated by the risk of electric shock for people and animals near 6-35 kV overhead lines. It is necessary to find the short circuit location in distribution networks in the shortest possible time. Inspection of extensive, branched and hard-to-reach overhead sections takes a lot of time, so it is easier and quicker to use special portable devices for search of ground fault location. As operating experience shows, search devices produced in Russia fail to determine location of “non-metallic” single-phase damage. The aim of this study is to identify the causes for failures of existing portable devices and to develop new ways of searching short circuit location. For this purpose, operation of 6-35 kV distribution network at different single-phase faults is analyzed. An equivalent circuit of the studied distribution network has been developed during the analysis. The authors have also completed a series of calculations of tension and currents of different harmonic components in network branches at different types of single-phase damages. They have studied the influence of resistance change in the place of short circuit on harmonic tension and current components and estimated emission of electromagnetic field under real overhead wires of the studied network at artificial single-phase damages. Cumulative amplitude-phase analysis of the highest harmonic current and tension components enables development of a new way of searching for ground fault location in the extensive 6-35 kV overhead distribution network. The main reason of failure of portable searching devices appears to be a level in-time variation of the highest harmonic current components.