An earth fault location method based on negative sequence voltage changes at low voltage side of distribution transformers

Abstract

The paper presents a new approach for earth fault localization which is based on evaluation of phase to ground voltages recorded by voltage monitors installed at low-voltage side of distribution transformer station deployed under smart metering projects. The introduced method “Vdip” determines the probability of asymmetrical fault location based on comparison of the changes in negative sequence current recorded at the feeding medium voltage substation and changes in negative sequence voltages recorded at the LV sides of distribution transformers. The paper describes the nature of the method and presents its principle using simulation of a MV resonant earthed distribution network where short-term connection of an auxiliary resistor is used. The method was also evaluated in real resonant earthed 22 kV network, where totally 15 earth faults with fault resistance up to 1.2 kΩ were carried out. As the result of this field test, the location error of the Vdip method is presented.