Two-Element Mixed Natural Ester Insulation Oil Doped with KH550-TiO2 Nanoparticles for Enhanced Antiaging Properties

Nanoparticles are presently considered to be high-potential additives in insulation materials. Surface modifiers can not only improve the compatibility between nanoparticles and natural ester but also enhance the insulation performance of the insulation liquid. In this work, a mixture of two natural ester insulation oils (rapeseed oil + palm fatty acid ester) doped with 3-aminopropyltriethoxysilane (KH550)-TiO2 nanoparticles was prepared, and a 56-day thermal aging experiment was implemented. Moreover, the molecular dynamics simulation was applied to investigate the improvement mechanism of the physicochemical and electrical properties from a microscopic perspective. The experimental results revealed that KH550-modified nano-TiO2 particles could reduce the generation of microwater and acidic substances during the aging process of the oil–paper insulation system, retard the degradation of the system, and improve the thermal stability and insulation performance. At the end of the thermal aging, a decrease of breakdown voltage by 7.3% and an increase of acid value by 17.3% were observed in the modified insulation oil. On the contrary, the pure insulation oil decreased the breakdown voltage by 26.96%, and the acid value increased by 28.38%. Furthermore, the molecular simulation results determined that KH550-TiO2 could combine with polar molecules through hydrogen bonds, adsorb polar molecules in insulation oil, prevent their diffusion into cellulose insulation paper, and delay the aging and decomposition of insulation paper. Therefore, the modified nanoparticles have remarkably enhanced the antithermal aging performance of the oil–paper insulation system, which provides a considerably greater application prospect for nanomodification insulation in liquid medium.