Establishing and optimizing the thermal path model of transformer temperature field is an important way to analyze the hot spot temperature of transformer windings. In the process of improving the thermal path model of oil-immersed transformers and improving the accuracy of their models

the determination of thermal resistance parameters of insulating paper is particularly critical. In order to analyze the case that the insulating paper and the copper contact interface are filled with the transformer oil

we observed the microstructures of insulating paper and copper surface by atomic force microscopy.According to the observation data

the contact thermal resistance model was improved

and the contact thermal resistance between the oil-impregnated insulation paper and the copper at d

ifferent temperatures was calculated. Therefore

we improved the dual heat flow meter method and tested the contact thermal resistance of copper and oil-impregnated insulation paper at different temperatures. The results show that the thermal resistance of copper and oil-impregnated insulation paper at 70 ℃ is calculated to be 0.000 541 m

2

·K/W and is tested to be 0.000 575 m

2

·K/W.As the temperature increases

the thermal conductivity of the oil-impregnated insulating paper decreases

and the thermal resistance of the contact between the copper and the oil-impregnated insulating paper becomes large. The average error between the experimental and theoretical values of the contact thermal resistance at five temperature points in the study is 6.49%. The research results provide a data support for establishing and optimizing the equivalent loop of the transformer thermal circuit model

and have good application value.