PRACTICAL HIGH-IMPEDANCE FAULT-DETECTION ON DISTRIBUTION FEEDERS

Distribution protection systems must balance dependability with securi ty considerations to be practical, This is quite difficult for high-im pedance faults, Only highly sensitive algorithms can achieve absolute dependability in detecting very low current faults, This high sensitiv ity results in a propensity for false tripping, creating a less secure system and resulting in the potential for decreased service continuit y and lower reliability, Researchers at Texas A&M University have bala nced fault detection with fault discrimination, resulting in a practic al combination of detection algorithms in a commercially viable system , This device has many ''intelligent'' features, including the ability to analyze and correlate numerous fault characteristics in real time, so that a correct determination of the status of the feeder can be ma de with a high probability of accuracy, This paper describes the use o f multiple algorithms to detect various types of faults and the use of an expert decision maker to decipher incoming data, to determine the status and health of a distribution feeder, Requirements for a practic al, secure high-impedance fault relay are also discussed. Finally, Tex as A&M has licensed this technology to a commercial partner, which man ufactures a device that detects high-impedance faults, in addition to performing numerous other monitoring and protection functions.