On the de-energization of over-head low-voltage lines under high-impedance fault conditions

Abstract

Downed distribution conductors in overhead distribution systems, may not be a concern for equipment, but greatly challenge the safety of persons, as well as the integrity of properties. Upstream overcurrent protective devices may not be able to detect the magnitudes of fault currents resulting from these high-impedance faults. Even though protective devices capable to detect such faults have been available on the market, not all the utilities have equipped their stations with these products, likely due to the costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for the low-voltage over-head lines with neutral wire. Such solution includes a metal hook underneath the line conductors, supported by the pole, and connected to the neutral wire. This arrangement would cause a line-to-neutral short circuit, positively activating existing over-current devices, which can therefore disconnect the supply. Costs and possible safety issues for workers related to the installation of the device to existing overhead lines are herein also delineated.