The influence of small molecule products on natural ester impregnated cellulose insulation paper under electric-thermal coupling field

Abstract

Transformer oil-paper insulation materials are vulnerable to insulation failure due to the influence of voltage, high temperature, and other complex conditions. Additionally, during the operation of the transformer, the generation of harmful substances such as small molecule acids and water becomes a significant concern. In this study, we employed molecular simulation technology to investigate the effect of small molecule products on natural ester-impregnated cellulose insulation paper under electric-thermal coupling field. The results show that: under the action of electric-thermal coupling, the introduction of the electric field can weaken the molecular thermal motion to a certain extent, and the higher the temperature, the more pronounced the weakening effect of the electric field. When subjected to an electric-thermal coupling field, the mean square displacement of the cellulose molecular chains inside the models doped with water and formic acid increases compared to the oil-paper composite model, with an increase of 60.13 % and 98.25 %, respectively, at 700 K. The fraction of free volume in the model increases and the cohesive energy density decreases, the diffusion ability of molecules inside the model remains strong. The weakening effect of the electric field does not diminish the hydrolysis reaction between the small molecular products and the cellulose molecular chains. This leads to a decrease in model stability and ultimately to the breakdown of the insulation paper.