Investigations on Novel Carbon Quantum Dots Covered Nanofluid Insulation for Medium Voltage Applications

摘要： The extensive use of mineral oil for high voltage insulation applications has directed to widespread research works targeted at improving its dielectric and thermal characteristics. The present study investigates a novel nanofluid insulation prepared using carbon quantum dots (CQD) which is used for the surface treatment of SiO2 nanoparticles added to commercially available mineral oil. The proposed nanofluid referred as CQD–SiO2 nanofluid is tested for its insulation properties such as AC breakdown voltage (BDV), partial discharge (PD), lightning impulse (LI), dissipation factor (Tan-delta), volume resistivity, viscosity and thermal characteristics such as flash and fire point. The tests were conducted for three different nanofluid concentrations, that is, 0.01%wt, 0.05%wt and 0.1%wt. Weibull distribution analysis is carried out for breakdown data of BDV test and LI test. Results of CQD–SiO2 nanofluid are compared with mineral oil with and without SiO2 nanofillers. The results show that inclusion of CQD covered SiO2 nanoparticles have the capability to improve the AC breakdown strength by more than 100%, partial discharge inception voltage by 50%, lightning impulse withstand capabilities up to 20% and volume resistivity by 50%. It has also the tendency to slightly improve the flash point and fire point properties than the mineral oil. Significant reduction of PD magnitude and Tan-delta values are noticed with CQD–SiO2 nanofluid. Such results indicate that the CQD–SiO2 nanofluid can be a suitable candidate for MV insulation applications.