"Large ground grid grounding resistance tester" is suitable for power sector, substation and other institutions of large-scale power grid grounding resistance testing test. At present, there are mainly two "large ground network grounding resistance testers" on the market. The "GYDW-II large-scale grounding network ground resistance tester" of Yiyi Technology Co., Ltd. is taken as an example, and an example is illustrated: one is: output current 3A, and the measuring range is: 0～200Ω. The other is: the output current is 5A, and the measuring range is: 0～200Ω. Substations have a lot of interference, so they use dual-frequency testing (45Hz, 55Hz, dual-frequency, sine wave), so that the instrument has strong anti-interference ability and accurate test values. The standard configuration of the test line is 300 meters and 400 meters, and there is no joint in the middle. Configure according to the diagonal of the power grid, tell the manufacturer of the area of the power grid, and make requirements with the manufacturer.