Molecular dynamics study on the diffusion behavior of furan molecules at oil-paper interface

The generation and diffusion mechanisms of furan molecules are crucial for understanding the dielectric properties of oil-paper insulation. Of particular interest, our focus here, is the diffusion behavior of furan molecules near oil-paper interface and how such behavior is influenced by different temperatures. Our oil-paper interfacial structures with dimensions of 26.7Å×26.7Å×56.7Å were constructed by Materials Studio using COMPASS forcefield. Furan molecules with a mass fraction of 5% were added to the cellulose layer in order to simulate their diffusion process near interface. The diffusion coefficient, interaction energy and number of hydrogen bonds, relative molecular concentration distribution as well as centroid trajectories of furan molecules were calculated. Our results show that the diffusion coefficient of furan molecules in oil-paper interfacial systems increases with the increase of temperature. This could be explained by our calculation results of hydrogen bonds and interaction energy between furan molecules and oilpaper insulation system. Moreover, the furan molecules are more likely to diffuse from cellulose paper into oil at higher temperature (above 750 K) due to the increased thermal motion of molecules, which can be illustrated by our calculations of relative molecular concentration distribution of furan molecules across the interface. Our findings above can provide a theatrical basis for DGA analysis for fault detection in oil-paper insulation.