在我国特高压交流试验示范工程中，晋东南1 000 kV变电站采用的1 100 kV 气体绝缘金属封闭开关设备（gas insulated metal-enclosed switchgear，GIS），为世界上首次投入商业运行的特高压交流GIS。该设备的接地系统设计，因其电压高、容量大而具有新的特点，结合施工条件提出了设置辅助地网的概念。通过对GIS的结构布置、接地点数目和可能通过的工频短路电流、雷电冲击电流和特高频电流大小的分析计算，最终确定了辅助地网网格大小。

In the first UHV AC testing demonstration project of China, 1000kV Jindongnan Substation adopts 1100kV gas-insulated metal-enclosed switchgear (hereinafter abbreviated as GIS), which is the first UHV AC GIS operating commercially in the world. Because of high voltage and large capacity, the design of the earthing system for this equipment possesses new characteristics, and concerning the actual construction conditions we proposed the concept of setting auxiliary ground grid. By analyzing and calculating the configuration of GIS, number of earthing point, power-frequency short-circuit current and lightning impulse current probably through, quantity of ultra-high frequency current, finally, we confirmed the size of the auxiliary grid. This article shows the earthing current value through each position of GIS and which is verified by current-resolution.