Shi, Huantong, Sun, Wei, Zhuo, Ran, Huang, Zhiming, Chen, Qiulin, Zhong, Lianhong, La, Yuan, Li, Xingwen, and Fu, Mingli
In power transformers, the degradation of the insulating oil due to aging, overheating, and electric discharge leads to the production of characteristic gases including H2, CH4, $\text{C}_{{2}}\text{H}_{{2}}$ , $\text{C}_{{2}}\text{H}_{{4}}$ , $\text{C}_{{2}}\text{H}_{{6}}$ , CO, and CO2. The composition and concentration of these gases provide valuable insights into the operational condition of the transformer. Dissolved gas analysis (DGA) is a vital diagnostic and predictive technique for transformer faults, which is closely associated with the transportation of gases in the oil through convection and diffusion. This study employs a combination of molecular dynamics simulation and experimental measurement to determine the diffusion coefficients ${D}$ of the seven characteristic gases in a naphthenic mineral oil across a range of temperature ( ${T}$ = 20 °–90 °C) and dc electric field strength ( ${E}$ = 0–3 kV/mm). The calculated and measured results of the diffusion coefficients exhibit a strong agreement, demonstrating a positive correlation with temperature following ${D}\propto \text{e}^{-\text {a}/\text {T}}$ , in which the influence from a weak dc electric field ranging from 0 to 3 kV/mm could be negligible.