Abstract: In order to deal with the problems of blind maintenance and inefficient resources that conventional transformer inspection techniques experience, an integrated technology system for the maintenance of equipment is proposed that combines condition assessment, fault diagnosis, on-line monitoring, and intelligent decision-making, based on the example of a 220 kV substation. By using multi-dimensional technology such as oil chromatography analysis, insulation diagnosis and partial discharge detection, the system can accurately assess the state of the equipment. The implementation was done without affecting the operation of the primary equipment. According to the operation data, the failure rate of the transformer was reduced by 65%, the number of unplanned outages was brought to zero, and the maintenance cost was reduced by 1.2 million yuan annually.