Method for high-impedance fault detection

Abstract

Correct detection of high-impedance faults (HIFs) is crucial because they produce a serious threat for humans, livestock and property. HIF currents, typically with fault resistances between 10 and 100 kΩ, cannot be detected with traditional protection functions and they behave randomly consisting of unstable and unpredictable dynamic fluctuations in the amplitude, harmonic levels etc. One main challenge is to reliably separate HIFs from normal network load and other switching events. In this study, new HIF detection method is proposed based on extensive power systems computer aided design (PSCAD) simulation studies and tests with real-life HIF measurements. The proposed method is applicable to different MV networks with different grounding practices. Depending on the grounding type, HIF detection is based on the use of zero sequence current I o or negative sequence current I 2. Method works in both 50 and 60 Hz networks and does not 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.