Performance Comparison of Environmental-friendly Natural ester Insulation Oil: Nano-SiO2 Modified with Different Functional Groups

As a foundational material in key fields such as ultra-high voltage (UHV) transmission, the performance of nanodielectrics directly impacts the efficiency and safety of crucial equipment. However, the molecular-scale microscopic mechanisms by which nanomodification enhances the thermal and dielectric properties of liquid insulating materials remain unclear. Understanding the principles underlying the performance enhancement of nano-modified insulating oils is crucial for ensuring the stable operation of UHV transmission projects. In this work, based on a natural ester insulating oil, nano-modified insulating oils doped with four types of surface-modified silica nanoparticles were prepared. The physicochemical and dielectric parameters under different doping concentrations were tested, and molecular dynamics simulations were employed to explore the interactions between different nanoparticles and the natural ester insulating oil under typical thermal fields. The results show that the enhancement effects of the three types of surface-modified SiO₂ nanoparticles on the properties of the natural ester insulating oil were significantly superior to those of pristine SiO₂. Surface modification improved the interfacial compatibility between the nanoparticles and the insulating oil, leading to more stable dispersion of the nanoparticles. This enabled the capture and subsequent release of more free electrons within the insulating oil, thereby inhibiting streamer initiation and propagation and enhancing the breakdown voltage. Molecular dynamics results revealed negative interaction energies between the surface-modified SiO₂ nanoparticles and the natural ester insulating oil, indicating an adsorption effect, with greater stability at elevated temperatures compared to pristine SiO₂ nanoparticles. Simulations of surface electrostatic potential and frontier molecular orbitals showed that the introduction of new modifying groups (–NH₂, –CH₃) on the surface-modified nanoparticles resulted in a strong positive electrostatic potential, allowing for the capture and release of free electrons, thereby delaying the generation and development of electron avalanches in the oil. This work integrates macroscopic characterization data with microscopic simulation parameters to elucidate the mechanisms by which surface-modified nanoparticles influence the stability of natural ester insulating oils, providing a theoretical basis and technical guidance for further enhancing the performance of natural ester insulating oils.