Wavelet transform based relay algorithm for the detection of stochastic high impedance faults

High impedance faults (HIF) are faults which are difficult to detect by overcurrent protection relays. This paper presents a practical pattern recognition based algorithm for electric distribution high impedance fault detection. The scheme recognizes the distortion of the voltage and current waveforms caused by the arcs usually associated with HIF. The analysis using discrete wavelet transform (DWT) yields three phase voltage and current in the low frequency range which fed to a classifier for pattern recognition. The classifier is based on the algorithm using nearest neighbour rule approach. A HIF model was also developed, where the random nature of the arc was simulated using MATLAB.