Performance testing of the Nordon high impedance ground fault detector on a distribution feeder

Distribution primary conductors which fault to ground rather than to the neutral conductor or other grounded object are known to result in fault currents which are too low to be detected by conventional overcurrent devices. Such faults, however, are shown to result in distorted currents which can be recognized as distinct from other distribution current distortions. The operating theory of a high-impedance fault alarm system (HIFAS) which can detect these low-current faults is presented. Procedures for safely conducting 13 kV line fault tests to confirm the performance of these new relay operating parameters without jeopardizing customer service are described. Test results that confirm the soundness of the detection principle are given