Research on Frequency Selection of Triple Frequency in Earth Capacitance Measurement

Abstract

AbstractThis paper investigates a frequency selection method of triple frequency in earth capacitance measurement. Based on the researches about the triple frequency method, the measurement principle of the proposed method is presented in detail. In this paper, the accurate earth capacitance in the distribution network can be calculated by establishing corresponding equations with injecting three different frequencies of current signals to the triangle open-side of voltage transformer (VT). Furthermore, the influences of selected frequency on the calculated results of the capacitive current are further analyzed. In order to improve the measurement accuracy, the initial selected frequencies of injected zero-sequence current signal should be set small as the larger earth capacitance in the distributed network is more common. Then the value of selected frequency should be increased correspondingly with the small capacitance in the distribution network. Finally, the correctness of theoretical analysis and feasibility of frequency selection method are verified with the simulation and experimental results of the earth capacitance measurement in distribution network.