Abstract: This paper analyses the correlation between abnormal changes in electrical and non-electrical parameters of transformers and their overheating defects. The results show that the growth of oil chromatography data and DC resistance are strongly related to the overheating defect. Among the non-electrical parameters, methane, ethylene, ethane, and hydrogen content in transformer oil increases abnormally, and micro-amounts of acetylene can be detected. Among the electrical parameters, the DC resistance increases. Furthermore, the oil chromatography data exhibits a growing trend with the transformer load. The study intends to provide a reference for overheating defects' detection, diagnosis, and causal analysis.

Keywords: transformer, overheating defect, indicator characteristics