Sankara SUBRAMANIAN, Krishnakumar VENKATARAMAN
ALSTOM Grid
UKHigh impedance fault (HIF) is generally defined as unwanted contact of an electrical conductor on a nonconductive surface like road, tree limb, sod or some other surface or object which restricts the fault current to a level below that can be reliably detected by conventional relays. Undetected HIFs such as downed conductors are rather dangerous for personal safety and property security. The primary objective of clearing a HIF is protection of personnel and property and not the power system. Therefore, HIF detection (HIFD) is of crucial importance for utilities and protection engineers.
Detection of HIF has long since been of great challenge as well as interest for industrial and academic research. Generally, ways to detect such kind of fault are mainly focusing on waveform features. Harmonics feature such as 3rd harmonic’s amplitude and phase has been used by early researchers. However, harmonic should not be considered as a feature uniquely for HIF, moreover, the accuracy may be affected by the background harmonic source such as nonlinear loads.
