Abstract: A device can be used with a power transmission system that includes three section that are connected at a junction, each section being from a corresponding. An input interface receives measurements of voltages and currents carried out at one or more of the first terminal, the second terminal and the third terminal or positive sequence voltage and current phasors obtained from the measurements of voltages and currents carried out at one or more of the first terminal, the second terminal and the third terminal. A phasor calculation module calculates positive sequence voltage and current phasors from the measurements of voltages and currents carried out at a terminal of the power transmission system. A fault locator obtains the fault location based on the section with the fault, the positive sequence voltage and current phasors obtained for each terminal, and the positive sequence line impedance parameters of each section.

Abstract: A method and device can be used with a power transmission line. Pre-fault voltage and current phasors and during-fault voltage and current phasors for each of first, second, and third terminals are determined based on disturbance records. Using an assumed faulted section, values for a propagation constant of each section, a surge impedance of each section, and a fault location parameter are computed. The computing is based on simultaneously solving pre-fault and during-fault objective functions for the assumed faulted section with the computed pre-fault and during-fault voltage and current phasors. The pre-fault and during-fault objective functions are formulated based on equating junction voltages determined from two of the terminals, conservation of charge at the junction, and equating fault location voltages determined from one terminal and the junction. The values determined for the propagation constant, the surge impedance, and the fault location parameter can be compared with predefined criteria.