Diffusion mechanism of dissolved gases in transformer mineral oil under furfural effect

Abstract

Context

Dissolved gas analysis (DGA) technology is a crucial technique for evaluating the operational state of transformers by detecting characteristic gases dissolved in insulating oil. Notably, the aging of insulation paper generates both characteristic gases and furfural, which also dissolves into the oil. However, the influence of furfural on gas diffusion behavior remains unclear. This study systematically investigates the effects of different furfural concentrations (0%, 1%, 3%, and 5% by mass) on the diffusion behavior of characteristic gases in insulating oil using molecular dynamics (MD) simulations. By calculating diffusion coefficients, free volume, and interaction energies, the underlying microscopic mechanisms were revealed. The results indicate that increasing furfural content slightly raises the free volume of gas molecules, thereby facilitating gas diffusion. Furthermore, the binding energies between furfural and insulating oil, as well as between furfural and gas molecules, increase with furfural concentration—mainly due to van der Waals interactions between polar and non-polar molecules. This study provides theoretical insight into the diffusion behavior of characteristic gases in insulating oil containing furfural.

Methods

The MD simulations were conducted using Materials Studio 2023. The amorphous cell module was employed to construct insulating oil mixture models incorporating varying concentrations of furfural molecules, utilizing the COMPASS III force field. Simulation results yielded key parameters including the mean square displacement (MSD) of characteristic gas molecules and the fractional free volume (FFV) of the system. Intermolecular interaction energies were computed using a self-developed Perl script. The simulation results demonstrate that increasing furfural concentration in insulating oil significantly enhances the diffusion characteristics of dissolved gases at the molecular level.