Estimating distance to transient and restriking earth faults in high-impedance grounded, ring-operated distribution networks using current ratios

Abstract

Earth faults occur frequently in distribution networks, and in resonant grounded networks they are challenging to locate precisely due to their naturally low fault current. Transient and restriking faults are more challenging still due to the short time available for the fault location logic, as well as the absence of steady-state conditions. This paper investigates the performance of three fault location methods utilizing the ratios of various current components in a network operated in a closed-ring configuration. A frequency dependent model of a distribution network is used to simulate transient and restriking faults, and both isolated grounding and resonance grounding are considered. The results show that fault location based on negative-sequence currents is able to locate transient faults, and its accuracy of a few hundred metres is comparable to what has been observed during permanent faults. A zero-sequence method is observed to be less accurate, particularly in resonant grounded networks. A transient method is also proposed, and while it is fast, it is ultimately limited by the presence of loads and branches in the network. It is concluded that the negative sequence method is best suited for transient and restriking faults.