Modeling of high impedance faults in electric distribution systems

A high impedance fault (HIF) is generated when an energized conductor (of a primary feeder) makes contact with the ground or with neighboring objects such as branch trees, overgrown vegetation, building walls, asphalt, any object to ground. Such faults are undetectable by conventional overcurrent devices such as overcurrent relays and fuses because their low current magnitude. Furthermore, arcing accompanies high impedance faults (HIFs) and represents a risk of security to people and damage to physical infrastructure. Thus, in order to obtain a trustworthy detection algorithm, it is necessary to have a reliable high impedance fault model. This paper presents an analysis of the HIF field test results and a methodology for modeling HIFs by considering a single nonlinear resistance to represent the fault. The methodology is implemented by using the MODELS section in ATP/EMTP.