Distribution networks HIF location: A frequency domain system model and WLS parameter estimation approach

High impedance fault location still represents a challenge for protection engineers. In this work, an analytical formulation for high impedance fault location in power distribution systems is presented, based on system parameters estimation. The proposed method is based on a frequency domain system model, developed considering a high impedance fault model composed by two antiparallel diodes and an arc resistance. The proposed model is an overdetermined nonlinear algebraic system of equations in which the solution is obtained through a Weighted Least Square approach. A residual analysis is applied for estimate selection. The proposed method considers the capacitive effect through an exact line segment model for overhead distribution lines, using only local voltages and currents as input data. Validation is done through numerical simulations using the IEEE system 13 buses test feeder, a real distribution system from the RGE Sul Power Utility (Southern Brazil), and a real high impedance fault recorded from a digital relay. Comparative test results with the state-of-the-art highlights the method's high accuracy, indicating potential aspects for real life application. Overall average errors of 0.3% considering a complete HIF model were obtained, and a 1.39% error considering a real HIF in a rural feeder. The formulation is currently used by protection engineers at RGE Sul as a reliability oriented tool.