Security testing of high impedance fault detectors

The security of high-impedance fault (HIF) relays is examined. Waveforms of HIFs as well as loads that behave to appear like HIFs were collected and processed. The detection parameters used in a number of present HIF detection algorithms were extracted and compared to test the algorithms' ability to discriminate between faults and fault-like loads. It was found that there are loads that imitate HIFs, and that the present algorithms lack the security required under these load conditions. The high-impedance fault-like loads considered were: an arc welding machine; a personal computer; and a fluorescent light. It was found that arc welders can easily imitate HIF conditions, and that the tested algorithms showed insecurity when tested with an arc welder load.<>