Novel fault location method for double-circuit three-terminal lines

This paper presents a new fault location method for double-circuit three-terminal lines based on the negative sequence network. The proposed method utilizes local voltage and current phasor measurements of both faulty and healthy lines at the relay location to calculate the fault distance. To detect the faulty branch beyond the branching point, it needs only the estimated fault location by the fault locator installed at one of the remote terminals. Besides, the derived formulation can be effectively used for all types of unbalanced faults. This method is based on the fact that the negative sequence voltages of the adjacent lines are equal to each other at the local and remote substations. The presented fault location algorithm is straightforward, and it can be easily implemented in practical applications. To evaluate the proposed method's performance, a test system is simulated under different fault conditions in the PSCAD/EMTDC environment. Using extensive simulation studies, the effects of fault resistance, voltage level, source impedance, line length, type of transposition, arc fault, measurement errors of line parameters, and impedances of line branches on the performance of the proposed method are investigated. Moreover, the framework of the established fault location scheme has also been investigated for the double-circuit two-terminal lines. The simulation results indicate the high accuracy of the proposed method, specifically for the faults after the branching point, covering the weakness of the traditional methods.