Dielectric and Thermal Response of TiO2 and SiC Natural Ester Based Based Nanofluids for Use in Power Transformers

The improvement of dielectric and thermal properties of insulating oils used in High Voltage (HV) equipment has been a key part of research over the last three decades. In this study, a natural ester oil is used as matrix oil and dispersions of two semi-conducting nanoparticles (NPs), titanium oxide (TiO2) and silicon carbide (SiC), are prepared in 0.004 weight percentage ratio (0.004% w/w). In terms of thermal features, thermal diffusivity and thermal conductivity are measured over a large temperature range between 25 and 90 degrees C. By means of the dielectric properties, the Lightning Impulse Breakdown Voltage (LI BDV) of nanofluids (NFs) is measured and compared to the corresponding ones of the matrix. Moreover, the dielectric constant and dielectric dissipation factor (DDF) are determined for the NF and matrix samples in the frequency range of 1 to 10(6) Hz. The obtained results show that the NF containing SiC NPs is characterized from the greatest increase in thermal conductivity, by 58% with respect to natural ester oil's, as well as the lowest dielectric constant in both 25 and 90 degrees C, most likely due to their higher permittivity and thermal conductivity. Lastly, the LI BDV of the same NF is the most enhanced, by 10% relatively to the matrix, while a numerical model in COMSOL Multiphysics is developed and is found to successfully verify the LI BDV results.

Automated summary

This study investigates the dielectric and thermal properties of insulating oils used in high voltage equipment. Natural ester oil is used as the base oil, and dispersions of titanium oxide and silicon carbide nanoparticles are prepared. The results show that the nanofluid with silicon carbide nanoparticles has the highest thermal conductivity and the lowest dielectric constant.