Molecular Dynamics Simulation of the Decomposition and Gas Generation Characteristics of Natural Ester Insulating Oils Under Overheated Conditions

Abstract

Natural ester insulating oils are increasingly replacing mineral oils as the insulating medium for oil-filled equipment due to their high ignition point, biodegradability, and other environmentally friendly properties. However, the reaction characteristics of natural ester insulating oils under different types of faults require further investigation. This paper presents the development of a molecular dynamics model employing the ReaxFF reactive force field to comprehensively simulate the decomposition of natural ester insulating oils over a temperature range of 2800–4000 K, elucidating the resulting product information. The gas production behaviour of natural ester insulating oils was examined under different overheating conditions and heating times. The simulation results indicate that the thermal decomposition products of natural ester insulating oil primarily consist of seven gases, including H₂, CO, CO₂, and others. Notably, the concentration of C₂H₄ gas exhibits a significantly nonlinear negative correlation with overheating conditions. Because of variations in simulation temperatures, the characteristic gases generated during the thermal decomposition of natural ester insulating oil correspond to different fault types observed in real-world scenarios. Specifically, the gas production at a simulated temperature of 4000 K aligns with the gas production behaviour of insulating oil during discharge fault events in practice. The results of this study offer a theoretical basis for the application of insulation condition monitoring in oil-filled equipment through dissolved gas analysis (DGA).