Zhejiang Province is located in a climate zone transitioning from temperate zone to subtropical zone. The climate is mild and the rainfall is moderate. 60% of the rainfall in a year occurs in May to September. During the rainy season, the environmental humidity is relatively high. At present, the outdoor terminal boxes, control cabinets, and institutional boxes (hereinafter referred to as cabinets) in the maintenance company are prone to moisture during the rainy season and day and night alternates, with high humidity and condensation, which are likely to cause safety hazards like equipment insulation degradation. At present, outdoor cabinets are mainly dehumidified by heaters, some cabinets are equipped with condensation dehumidifiers, and very few cabinets are equipped with cabinet air conditioners to dehumidify and prevent condensation. From the perspective of daily operation, condensation still occurs in most of the cabinets of the substation. There are water droplets on the observation window, inner wall and top of the cabinet, which causes the exposed metal parts like terminal block bolts to be corroded, which easily causes the internal relay of the equipment, abnormal conditions such as contact damage, DC grounding, switch malfunction, seriously affecting the safe operation of primary equipment.