Algorithms for locating current and voltage signal in a single phase-to-earth fault in distribution overhead networks

Overhead networks in the medium voltage range (6–35 kV) are the least reliable component in the process of electric power supply to consumers. Single phase-to-earth faults (SPEF) are the most widespread failures in such networks. Unlike short circuit in networks with grounded neutral, the singularity of a single phase-to-earth fault is a small emergency current relatively phase load current, which impedes its identification. To increase the reliability of detecting the commencement of an SPEF, this paper considers transition current and voltage signal separation algorithms implemented by digital filters (DF). To develop the DF algorithms, phase current and voltage oscillograms registered at power transmission lines during an SPEF using a digital oscillograph were analyzed. The DF amplitude-frequency characteristics for different algorithms are plotted. It is shown that, at certain parameters, the DF amplitude-frequency characteristic is optimally matched with the spectrum of the transition process. Thus, the reliability of detecting the commencement of an SPEF from the “signal/noise” criterion is increased.