In order to solve the problem of transformer insulation decline, Jiaxing Electric Power Bureau decided to adopt on-site vacuum drying treatment. According to the actual situation of the site, two sets of drying schemes were formulated: firstly, the hot oil circulation vacuum drying method was adopted. If the effect was not obvious, the hot oil circulation spray vacuum drying method was adopted. The principle of hot oil circulation vacuum drying method, 80% of insulating oil is retained inside the transformer, and the oil is heated to about 95 °C, so that the dehydrated oil is heated into the coil through the strong oil passage, so that the water content of the oil is always maintained. Low level. In this case, the water molecules of the internal insulation of the transformer will continuously diffuse into the oil, and the insulation of the transformer can be continuously improved by repeated cycles of drying.