Abstract: This paper analyzes a case of heating jamming of high voltage bushing cap of main transformer in a 220 kV substation. Through on-site analysis, combined with the historical inspection data of primary equipment, equipment historical patrol records and infrared temperature measurement records, the accident is analyzed and summarized according to the causes of similar abnormalities of this type of equipment in the early stage. The cause of this event is not only related to the vibration of the equipment operating environment, but also related to the oxidation of the equipment itself caused by local overheating. This paper analyzes and puts forward treatment and improvement measures for such events, so as to avoid the recurrence of such events and improve the ability of stable and safe operation of substation.