Research on fault location online for neutral point ungrounded system

Fault location on line for distribution network is necessary with the improvement of demand for the reliability of the power supply.By analyzing the single-phase-to-earth fault of neutral-ungrounded system,this paper drew the relationship between the zero sequence current and the zero sequence voltage,and then proposed the method of magnitude and phase comparison which was implemented by using the mobile zero sequence CT and wide area phase measurement.The method takes advantages of three methods and has no influence by the system structure and little influence by the fault resistor.The method has been proved to be valid by simulation.