Single line-to-ground fault location based on unsynchronized phasors in automated ungrounded distribution systems

Abstract

This paper proposes a new method for locating single line-to-ground (SLG) faults in ungrounded distribution systems. A distribution automation system is required to obtain all the required information from feeder remote terminal units via a communication channel with unpredictable time delays. Before locating a SLG fault, the faulted section is identified based on the absolute difference between the approximate zero-sequence angles of two adjacent nodes. Fault location starts by obtaining the synchronized zero-sequence voltage and current at the faulted node. This is achieved by forward calculation from the zero-sequence voltage and current at the substation. Because the zero-sequence current at the faulted node is calculated in synchronization with the substation, the other phasors at the faulted node are synchronized by phase compensation based on the phase difference between the synchronized and measured phasors corresponding to the zero-sequence current. Using the synchronized phasors, the fault location is identified through application of an orthogonal operator to the voltage equation at the faulted node. The performance of the proposed algorithm was evaluated using fault signals generated by the EMTP. The simulation results confirmed the validity and efficiency of the proposed algorithm for locating SLG faults in ungrounded distribution systems.