Simulation Analysis of Earth Surface Potential Distribution in ±800kV HVDC Ring Grounding Electrode

This paper analyzes the regularity of +/- 800kV HVDC grounding current dispersal in 3 common types of circle Grounding Electrodes by simulating the earth surface potential(ESP) distribution. When HVDC system is in single pole operation mode then a large amount of current can be dissipated from grounding system. Firstly, a single line +/- 800kV HVDC transmission system is built in this paper to simulate the grounding current. The measured stable grounding current is 4000A. Secondly, a grounding electrode current dispersal model in 3-layer soil is designed and then inserted 4000A current in single ring electrode, double rings electrode and three rings electrode. After the analysis of simulations, it is proved that single ring electrode has the highest surface potential distribution . In the double ring grounding electrode, the ratio of inner and outer rings is preferably controlled at 0.7 to 0.75 to get a best current dispersal characteristic. This study provides valuable suggestions for design of HVDC grounding electrodes.