A Novel Unified Measurement Method for Ground Capacitance and Arc Suppression Coil Inductance of Resonant Grounding System

The accurate measurement of the ground capacitance is helpful to ensure the compensation effect of the arc suppression coil. To improve the accuracy of measurement, a unified measurement method for ground capacitance and arc suppression coil inductance based on signal injection method and fast Fourier transform (FFT) is proposed. Firstly, the relationship between the neutral voltage and the system parameters is established. Secondly, current at a specific frequency is injected into the neutral point, and the neutral voltage component at the specific frequency is obtained by FFT to eliminate the power frequency error. Then the unified measurement is realized according to the equivalent circuit. Finally, the proposed method is tested by the MATLAB/Simulink, which shows that this method is suitable for various types of arc suppression coils. In the three-phase asymmetry condition, the maximum errors of ground capacitance and arc suppression coil inductance are 0.1% and 0.11% respectively, and the maximum errors are 1.3% and 1.8% respectively in three-phase symmetry condition.