Detection of high-impedance faults in power distribution systems

When overhead power lines in solid or low-impedance grounded systems lose supports and fall on poorly conductive surfaces, they generate high-impedance faults (HIFs). These faults are a great public safety concern because the fault currents are generally too small for detection by conventional overcurrent relays. This concern has generated great interest in the detection of downed conductor-related HIFs at the substation level. In this paper, we present an HIF detection algorithm that uses traditional relay logic. The algorithm is easier to understand and simpler to implement than many black-box detection methods such as neural networks. We discuss such key aspects of algorithm design as input quantity selection, generation of a reliable reference, adaptation to feeder ambient load noises, and decision logic based on trending and memories. We use real-world data collected from staged HIF tests and noisy substation loads to validate detection results.