Phase Asymmetry: A New Parameter for Detecting Single-Phase Earth Faults in Compensated MV Networks

Traditionally, the detection of high-resistance earth faults has been a difficult task in compensated medium-voltage (MV) distribution networks, mainly due to its very low-current fault. To date, several techniques have been proposed to detect them: using current injection in the neutral, superposing voltage signals, varying the value of the arc suppression coil, etc. These techniques use different detection parameters, such as fault resistance to earth, line asymmetries, or partial residual neutral voltages. In this paper, phase asymmetry is defined as a new parameter that can be used, together with the aforementioned techniques, in order to improve the reliability and efficiency of the detection process in single-phase earth faults, especially for compensated networks. The use of this parameter has been validated through extensive simulations of resistive faults up to 15 k Omega, with the use of RESFAL software, which is based on Matlab/Simulink.