Design and implementation of an adaptive High Impedance Fault relay

To maintain both dependability and security, high impedance fault (HIF) relays must have a good discrimination between high impedance faults and any no fault condition on the feeder that the relay is installed. As these types of faults exhibits very low magnitude currents, the discrimination methodologies are mostly based on the contents of current waveforms; in order to reveal any kind of distortion. Accordingly, the settings of IIIF relays can not be determined by simple readings from the meters on the feeder, but they must be found through comprehensive simulations of different necessary conditions on the feeder under consideration. In this paper, an operational procedure in conjunction with a novel computational algorithm is proposed that has solved the problem of determination of HIF relays settings. The discrimination is based on the magnitude, randomness and steadiness of harmonic energy content of the current waveform. The proposed algorithm does not need any initial information from the distribution network and therefore is adaptive and treats automatically.