A parametric digital signal processing algorithm for arcing high impedance fault detection

Abstract

There is a problem which currently exists in the electric utility industry with the detection of high impedance faults. A high impedance fault is one which does not draw sufficient fault current to be detected and cleared by conventional overcurrent protective devices. Arcing is usually associated with these faults which may cause damage to public property and hazard to personnel safety. Several solutions have been proposed to detect these faults over the past few years. Although a few schemes show promising potential, none to date has proven to be the final answer. A detection scheme which uses a technique that is powerful for a given system condition is found to be lacking for a different circumstance. This research concentrates on understanding the behavior of these faults under widely varying conditions. An effort has been made to investigate in a statistical manner specific behavior characteristics such as arc duration, arc repetition rate, and dependency of several spectral magnitudes on burst duration, soil type, and system configuration. Based on the characteristics, electrical parameters are identified for use as potential fault indicators. A vectorial fault detection scheme that utilizes a multi-parameter fault vector is presented to identify these faults. Confidence factors are associated with the detection parameters to determine their level of confidence. Two methods are outlined to evaluate the confidence factors. A criterion function is suggested to correlate the parameters of the fault vector. A technique is presented to monitor the criterion function in a statistical manner to make the necessary discrimination between an arcing fault and a feeder switching event. A method is also presented to evaluate the fault direction using several parameters after the presence of one has been detected. The statistical distributions of the parameters are presented along with their dynamic ranges under normal and fault conditions. A system architecture is suggested for the arcing fault detector and the signal conditioning requirements enumerated.