Detection of places of single-phase ground fault by frequency of the resonance

Abstract

Long-term single-phase ground fault in overhead 6-35 kV power lines with isolated neutral, accompanied by intermittent arc, lead to overvoltage and damage of electrical equipment. In turn, precise localisation of the damaged sections of the overhead power lines is a challenging task, as external inspection of power lines takes a lot of time, effort and resources, depending on the surrounding conditions or the access difficulty of the lines. The present paper proposes to apply the theory of using the property of long lines - to increase the voltage at the open-circuit, when the length of a transmission is quarter of a wavelength. The analysis of the conducted research has shown that the higher harmonics generated by the arcing fault on certain frequency serve as a source of voltage increase at the step-down substation. In addition, frequency and amplitude of the "resonance" harmonics allow identifying the damaged area of the power line in the electrical grids with tree-like topology.