Effect of Zirconia Nanoparticles on the AC Breakdown Voltage of Mineral Oil, Synthetic, and Natural Esters

This article aims to study the ac breakdown voltage (ac BdV) in mineral oil, synthetic and natural esters (NEs), and corresponding nanofluids (NFs) with dioxide zirconium (ZrO2). The ac BdVs of pure liquids are compared with the corresponding NFs for five concentrations ranging from 0.1 to 0.5 g/L. The ac BdV test is carried out according to IEC 60156 standard on a sphere-to-sphere electrode configuration with a 2.5 mm distance spacing. First, a statistical
${t}$
-test is performed on the experimental outcomes to inquiry the statistical differences/in-differences on the mean ac BdVs of base liquids and corresponding NFs with different concentrations; the results show that, except for NE-based NFs with the concentrations 0.1 and 0.2 g/L, the mean values of all NFs differ from those of base liquids. Then, the mean ac BdVs are compared with those of base liquids. The results show that the optimal concentration in the case of mineral oil based-NFs is 0.2 g/L (17.26% of improvement), while with synthetic and NEs, the optimal concentration is 0.4 g/L (13.34% and 8.39% of improvement, respectively); NE-based NFs with the concentration 0.1 and 0.5 g/L showed a reduced ac BdV compared to base liquid. Finally, goodness-of-fit tests are performed on the ac BdV to assess whether the experimental data obey the Weibull distribution law; and the curve lines are then used to determine the ac BdV at 1%, 10%, and 50% risk levels. The results show that adding ZrO2 NPs positively impacts the BdVs at low-risk probabilities.