Study on Physical Properties of Liquid Crystal Based FR3 Insulating Oil

Natural ester insulation oil has both the high environmental friendliness required by the dual carbon strategy and the high ignition performance required by fire safety. As a type of natural insulation oil, FR3 insulation oil is suitable for transformers exceeding 110 kV, especially for high-voltage insulation equipment. To further improve the performance of FR3, two nematic liquid crystals (4-Butyl N-(4ethoxybenzylidene) aniline (EBBA LC) and 4’-[(S)-2Methylbutyl]biphenyl-4-carbonitrile (CB15 LC)) with good compatibility with FR3 were selected as functional modified materials. Subsequently, the physicochemical performance (pour point, flash point) of the FR3 natural ester modified with liquid crystals were evaluated. Results show that both two liquid crystal additives can improve the physicochemical properties of FR3. Especially the modified materials with a concentration of $0.5 \mathrm{vol} \%$ of liquid crystal exhibits the most outstanding performance improvement effect.