Patent ID: 9476930
Filing Date: 2016-10-25
CPC Classification: G01R,Y04S

Claim Text:
1. A method for determining a location of a fault in an ungrounded power distribution system, wherein the power distribution system includes a set of feeders connected to a substation, wherein each feeder includes a set of feeder sections, wherein each feeder section starts with an upstream switch and includes a set of loads connected by line segments and each line segment includes an upstream bus and a downstream bus, wherein the fault is a multi-phase fault including one of a phase-to-phase fault, a double-phase-to-ground fault and a three-phase fault, comprising: determining, for a feeder, a furthest feeder section with a current at an upstream switch above a threshold as a faulty feeder section; determining a faulty line as a lateral starting from a first bus of the faulty feeder section if the faulty feeder section lacks a downstream switch, as a lateral starting from a faulty bus on a mainline of the faulty feeder section between the upstream and the downstream switches of the faulty feeder section if a voltage of the faulty bus determined based on measurements of the upstream switch approximately equals a voltage of the faulty bus determined based on measurements of the downstream switch, or as a the mainline; determining the location of the fault at the first bus or at the faulty bus if the lateral has only one bus; determining, if the faulty line is the lateral and the fault is the phase-to-phase fault or the double-phase-to-ground fault, the location of the fault at a first point on an un-faulty phase of the lateral where a fault current equals a load current; determining, if the faulty line is the lateral and the fault is the three-phase fault, the location of the fault at a point with a difference between imaginary parts of equivalent fault impedances at three phases below a threshold; and determining, if the faulty line is the mainline, a faulty segment of the faulty line between an upstream bus and a downstream bus having voltages with substantially opposite phase angles, and determining the location of the fault at a point partitioning the faulty segment on two sub-segments with a ratio of lengths determined based on the voltages at the upstream and the downstream buses, wherein steps of the method are implemented using a processor.