Straightforward Detection Method for High-Impedance Faults

Abstract

High-impedance faults (HIFs) caused by fallen energized overhead lines (downed conductors) produce a serious threat for humans, livestock and property. Therefore, correct detection of HIFs is crucial for whole society. HIF current, 0.01-100 A, is in the range of load current and cannot be detected with traditional protection functions. Each HIF is also different, behave randomly and may be difficult to separate from normal network switching events. Therefore, many previous HIF detection methods over past decades have been based on adaptation, learning and on utilization of multiple algorithms. However, many of these methods are not suitable for tripping operation and can be only used as alarming HIF functions due to rather slow or complex decision logics and sensitivity to false detections. In this paper, new HIF detection method is proposed based on extensive PSCAD simulation studies and tests with real-life HIF measurements. The proposed method works in both 50 and 60 Hz networks and doesn’t need voltage measurement. It also works as tripping protection function with sufficiently short operation time, is simple/flexible and has good usability from end user point of view. It is applicable to low-resistance and solidly grounded MV networks.