Abstract:When the GIS operating under industrial frequency voltage is invaded by trace water， the insulating property of SF₆ gas inside the gas chamber will be seriously reduced，which will affect the safe operation of high-voltage electrical equipment. For this reason，the GIS insulation structure experimental device is designed independently，and the frequency experimental research on SF₆ gas under slightly uneven electric field is carried out by constructing the gas discharge experimental platform and controlling the distance of the discharge gap，air pressure and different micro-water content. The results show in a slightly uneven electric field，the frequency insulation performance of SF₆ gas decreases with the increase of micro-water content；when the gas pressure is set to 0.4~0.6 MPa，the micro-water content is more than 800 μL/L，and the frequency breakdown voltage of SF₆ gas decreases more obviously；under the same gas pressure，the larger the gap distance is，the effect of micro-water content on the frequency insulation performance of SF₆ gas is the more obvious. In addition，based on the experimental results，450 μL/L and 250 μL/L were suggested as the moisture control limits at 0.4 MPa，0.5 and 0.6 MPa at 15 ℃，respectively，under the IFV voltage.