Optimization Study of GIS Grounding Grid under Disconnecting Switch Operation Based on ATP-EMTP

When the gas insulated switchgear (GIS) performs routine isolating switch operations, arcs will be generated at the switch connections. The disturbance voltage between the busbar and the short lines will be continuously reflected, generating high-frequency transient overvoltages and strong transient currents diffused to the grounding network at the grounding point, threatening the safe operation of the grounding network. In order to quickly dissipate the short-circuit current in the limited area of the grounding network, the grounding network needs to be optimized and designed. Firstly, the models of the internal and external part of GIS as well as the grounding grids are established by using ATP-EMTP electromagnetic transient simulation software. The simulation was carried out for the installation of vertical grounding body under the condition of multilayer soil, and the influence of the vertical grounding electrodes on the impact dissipation characteristics of GIS grounding device was studied. The grounding resistance before and after installation was calculated and compared to obtain the final optimized solution of the grounding grid. The results show that for multilayer soils, using unequally spaced grounding grids combined with increased vertical grounding electrodes can effectively stabilize the ground potential distribution and achieve the best resistance reduction effect, providing a theoretical basis for GIS grounding design.