This product applies oil-immersed explosion-proof device and kerosene gas phase drying method to dry. It has the functions of explosion-proof, large-capacity protection, online monitoring of typical faults and others. It has the characteristics of short circuit resistance, high insulation, excellent temperature rise and high error accuracy. The product has been used in key projects at Wunan, Jiangsu Province, Daqing Substation, Heilongjiang Province and other places.