A combined and improved fault line selection method for non-solidly earthed network

Based on the traveling wave theory, the process of transient traveling wave in non-solidly earthed network has been analyzed. The analysis discovers that the traveling waves in the healthy lines are mainly composed of the refracted traveling waves at the bus bar, which are generated from the backward traveling wave of the fault line, then the energy of the refracted traveling waves is the main portion of that in the healthy lines; the energy of the transient traveling waves in fault line is much more than that in the healthy lines, and a thought that peak values are used to express the traveling wave energy is proposed. Considering the complicated conditions in practical field, line selection error may occur only using one criterion, especially in high resistance fault and zero crossing fault. Fractal theory has the superiority in signal fluctuation detection, a combined criteria based on energy of traveling wave and fractal theory is composed in this paper. The ATP simulation shows that the combined criteria improves the robustness, and has high adaptability.