Resonance Analysis of Small Current Grounding System in Distribution Network

At present, there are a large number of arc suppression coil grounding mode in the low-voltage distribution network for the equipment insulation and power supply reliability considerations. The role of arc suppression coil grounding mode is when the grid single-phase ground fault occurs, arc suppression coil will provide inductor current to compensate the capacitor current. It is conducive to prevent the arc-reignition, to achieve the purpose of arc extinguishing, which will reduce the high amplitude over-voltage probability, to preventing further expansion of the accident. Engineering is generally used the overcompensation method for the wayto prevent the occurrence of resonance phenomenon. But, the capacitive current data used in the overcompensation method of the engineering are generally designed to be estimated based on recent or long-term loads and current equipment conditions. In the following years of substation operation, due to the rapid increase in load, the rapid expansion of the transmission line, the actual capacitor current is often quite different with the originally estimated one. Especially for large-scale urban distribution network with large number of cable or large-scale overhead lines to transform the cable, the design of the over-compensation mode of operation may no longer be established, become fully compensated or even under-compensation. Several obvious voltage waveform distortion of the actual distribution network is analyzed in this paper. The resonant energy spectrum of each phase is analyzed by MATLAB, and it is pointed out that the resonance of the voltage waveform is caused by the resonance of the zero sequence circuit. And use RTDS simulation system to modeling and analysis this situation. The simulation results are in good agreement with the actual waveforms, which will verified that the results of this paper are correct.