Patent ID: 7233153

Claim:
A method for determining a location of a phase-to-earth fault in a three-phase electric line of an electric network, the electric line comprising two or more sections, each section having a predetermined positive sequence reactance and an earth return path reactance, the method comprising: detecting a phase-to-earth fault on the electric line; identifying a faulted phase of the electric line; determining, at a measuring point, a reactance of a fault loop formed by the phase-to-earth fault, determining a faulted section of the electric line to be a section closest to the measurement point of all such sections for which a sum of a positive sequence reactance and an earth return path reactance of the section in question and positive sequence reactances and an earth return path reactances of sections, if any, between the measurement point and the section in question is greater than or equal to the determined reactance of the fault loop; and calculating a distance D between the measuring point and a point of fault according to the following formula: D=D p +(( X Loop −X P )/ X F )· D F , where X Loop =reactance of the fault loop X P =sum of the positive sequence reactances and the earth return path reactances of sections, if any, between the measurement point and the faulted section of the electric line, X F =sum of the positive sequence reactance and the earth return path reactance of the faulted section of the electric line, D P =sum length of the sections, if any, between the measurement point and the faulted section of the electric line, and D F =length of the faulted section of the electric line.