High impedance fault detection implementation issues

Faults on distribution circuits are normally detected by simple overcurrent relays. Faults through a high impedance such as dry earth or asphalt do not have sufficient current to operate overcurrent relays and must be cleared manually. Such high impedance faults may pose a hazard to the public. Equipment is now commercially available to detect a high percentage of high impedance faults, but use of this equipment introduces operational issues which affect applications. This paper discusses technical as well as nontechnical issues associated with applying high impedance fault detectors. Recognizing all the issues is important to the effective implementation of these new fault detecting techniques.