Investigation on Cold Flow Properties of Natural Ester Insulating Oils Based on Molecular Dynamics

Natural ester electrical insulating liquids constitute a suitable alternative to mineral insulating oils. However, the poor cold flow properties of natural ester insulating oils are a bottleneck limiting the use of transformers filled with natural ester insulating oils in cold environments. The relatively high pour point of natural ester insulating oils can negatively affect the low-temperature cold start of offshore wind transformers. This article investigates the cold flow properties of natural ester insulating oils by molecular dynamics simulation. First, four major molecules (tristearin, triolein, trilinolein, and trilinolenin) in soybean-based natural ester insulating oils were optimized using density functional theory (DFT), with relative contents of 16%, 24%, 50%, and 10%. Second, a model of natural ester insulating oil with a total of 500 molecules was constructed by the Packmol program. Finally, we used the general amber force field (GAFF) to carry out the molecular dynamics simulation. This study experimentally verifies the accuracy of the simulation results, makes up for the shortcoming of measuring the density of natural ester insulating oils in cold environments, and provides a convenient and low-cost method for predicting the pour point of natural ester insulating oils. It also predicts the pour point of natural ester insulating oils mixed in various proportions, which guides in finding a natural ester insulating oil with excellent cold flow properties. It helps to break through the technical bottleneck of the application of natural ester insulating oil in cold climate environments.