Molecular Mechanism of Ester Insulating Oil Improving Intrinsic Aging Resistance of Oil-Impregnated Paper Under Combined Electro-Thermal Effect: A new perspective

The aging of the oil-paper insulation system of the transformer is the key factor affecting its life. Existing studies primarily focus on the role of ester insulating oils, often overlooking the impact of insulating oil on the intrinsic properties of oil-impregnated paper once it permeates the insulating paper to form an oil-paper composite structure. Based on the molecular level, this paper proposes a novel perspective on the mechanism by which ester insulating oil enhances the intrinsic aging resistance of oil-impregnated paper. Using molecular dynamics theory, simulations of two oil-impregnated paper models were conducted. Within the temperature range of 303 K to 393 K and electric field intensities of 0–30 kV/mm, the self-diffusion coefficient, isobaric heat capacity, hydrogen bond count, hydrogen bond lifespan, and cohesive energy density of the two oil-impregnated papers are analyzed. The results reveal that, under the combined effects of electric and thermal stresses, ester oil-impregnated paper exhibits superior stability, thermal conductivity, hydrogen bonding, and mechanical properties compared to mineral oil-impregnated paper. Consequently, ester insulating oil enhances the intrinsic resistance of oil-impregnated paper to both electric and thermal aging. This study provides a new perspective to understand how ester insulating oil delays the aging behavior of oil-impregnated paper, which provides a theoretical basis for extending the life of transformers.