Abstract: This paper introduced a practical case of 220 kV combination appliance bus bellows heating.First of all, combined with the structure of the bellows, it proposed two possible causes of heating, circulation heating and conductor heating, and compared the temperature characteristics of the two types of heating through theoretical analysis.The difference was then compared with the on-site infrared temperature measurement map, and further dismantling and inspection of the heating part was carried out.Finally, the cause of heating was determined to be poor contact at the conductor connector plug.After that, by establishing a three-dimensional simulation model of the same structure, the temperature characteristics of the bellows when circulating current heating and conductor heating were simulated and calculated.The conclusions drawn were consistent with the analysis results in the case, which verified the correctness of the case analysis process and results, and had a certain reference for the identification and diagnosis of the same type of faults.