Power transformers always experience problems such as ageing, overheating or discharging faults during the process of the transformer, resulting in the decomposition of the insulating superheating paper and the insulating oil. This phenomenon leads directly to the generation of dissolved gases in the oil, which diffuses through the oil and then reaches equilibrium. In this paper, molecular dynamics is the main focus. The amorphous crystals of cycloalkyl oil and small molecules of characteristic gases are established by using Materials Studio software. The diffusion behaviour of small molecules in cycloalkyl oil is simulated and the mean square displacement of characteristic gases is calculated by using COMPASS force field. According to Einstein's equation, the relationship between mean square displacement and diffusion coefficient is obtained. The intensity of diffusion ability of the characteristic gases in the cycloalkyl oil is obtained by comparing seven different characteristic gases and seven diffusion coefficients of different characteristic gases. The effect of temperature on the diffusion ability of small molecules with different characteristics in naphthenic alkyl oils was studied by setting different temperatures. The diffusion law of typical characteristic gas in insulating oil is discussed, which provides a theoretical basis for improving DGA technology, in order to improve the accuracy of DGA technology in transformer fault judgment.
