Thermodynamic Study of Transformer Oil Thermal Decomposition Gases Considering Temperature Effects

Dissolved Gas Analysis (DGA) in transformer oil is widely applied in the fault diagnosis of oil-immersed power transformers. Currently, research on dissolved gases focuses on revealing the microscopic dynamic characteristics of gas generation in oil through atomic-level molecular dynamics simulations, but is limited by the rationality of the established systems. In this paper, starting from a thermodynamic perspective, the temperature-dependent characteristics of thermodynamic parameters such as heat capacity, enthalpy change of reaction, and equilibrium constants are fully considered. Numerical calculations of dissolved gases in transformer oil are performed based on the theory of chemical equilibrium constants. Using 1 mol of propane as a typical alkane molecule for calculations, the results indicate that in the thermal cracking reactions of alkanes, chain-breaking reactions occur first with increasing temperature, followed by dehydrogenation reactions, producing small-molecule alkanes, alkenes, alkynes, and hydrogen. The evolution of the molar fractions of each substance aligns well with the actual gas content in the oil, providing a solution for calculating dissolved gases in oil.