ABSTRACT
Water content in insulating oil used for transformers is one of the crucial reasons accounting for its insulation deterioration. Lots of experiments were carried out to study the water influence on dielectric properties of oil insulation, but little is known about the mechanisms behind it, especially at the molecular level. To this end, the diffusion behaviors of water molecules in mineral and vegetable oil were studied by the molecular dynamics approach. The relation between different mass fractions of water content (1%, 3%, and 5%) in mineral and vegetable oil and its diffusion coefficients were studied. We found that the higher the mass fraction of water content is (up to 5%), the smaller the water molecules’ diffusion coefficient is. In addition, this diffusion coefficient of water molecules has a greater value in mineral oil than that in vegetable oil when the mass fraction of water content is the same. These findings can be explained by our calculations of free volume fraction and the interaction energies.
