Two novel current-based methods for locating earth faults in unearthed ring operating MV networks

Abstract

Automated fault location plays a key role in improving the reliability of modern power grids—it helps to reduce the power outage time and the number of affected customers. Earth faults in isolated systems are among the fault types that are difficult to detect and locate with a reasonable accuracy, and there has therefore not been a well-established method for detecting and locating such faults in isolated systems. This paper presents two novel current-based methods for locating earth faults in unearthed closed-ring MV networks. The methods are based on the utilisation of sequence components of standard current and voltage measurement at a primary substation and they do not require new devices or measurements in the field. Both methods are tested with a simulation of a network based on data provided by a Norwegian network operator and their prediction performances were investigated considering different scenarios on fault resistance, load asymmetry and measurement errors. Both methods performed well and showed good accuracy. The simulation results are promising and strengthens the prospect of further testing of the methods in real networks and adoption of the methods for a real-world implementation. • Novel earth fault location method for ungrounded ring operating MV networks. • Earth fault location method utilising the ratio of change in negative sequence current. • Earth fault location by utilising the ratio of change in zero sequence current & voltage. • Equations for sequence currents & division of zero sequence current in ring network. • Robust fault location against fault resistance, load asymmetry and measurement errors.