Detection of single phase earth fault in compensated network with C0 estimation

Abstract

Single phase earth fault in compensated network creates faulty current with very small magnitude. The connection of a Petersen Coil in the transformer neutral turns the zero sequence impedance into very high ohmic system. The small faulty current makes the detection of the faulty feeder impossible with simple over current protection. That is why algorithms are using transients. This paper presents a novel method to detect such earth fault with a strong sensitivity regarding the fault impedance. The algorithm builds a model of the sound feeder behaviour using the zero sequence voltage and current. The healthy feeder can be considered as a zero sequence capacitance. By measuring the deviation of a perfectly capacitive feeder, the faulty one can be detected. Algorithm description and tests are presented with comparison of small impedance fault and high impedance with recordings and simulations.