Enhancing Thermal Performances of Synthetic-Ester Insulating Oil via Blending with Natural Ester

Abstract

In this study, natural ester insulating oil (FR3) is blended into the synthetic tetra-ester (KA) to enhance the thermal performance of the latter, typically increasing the flash point and fire point, at the same time, reducing the dissipation factor. The flash point (open cup), fire point, and pour point of the ester blends follow a quasi-linear relationship with the variation (in vol%) of FR3 except for the flash point (closed cup). The nonlinear behavior of flash point (closed cup) is confirmed by the results of thermogravimetric-derivative thermogravimetric-differential scanning calorimetry (TG-DTGDSC) in nitrogen. The optimized ester blend is with the content of 15 vol% FR3 which is manifested by high flash point (closed cup, $260^{\circ}\mathrm{C})$, high fire point ($312^{\circ}\mathrm{C}$), low dissipation factor (1.44%), low pour point ($51^{\circ}\mathrm{C}$), and high onset temperature of DSC either in nitrogen ($229.99^{\circ}\mathrm{C}$) or in air ($272.05^{\circ}\mathrm{C}$).