Due to environmental concerns and increased energy demand, natural esters are among the alternatives to mineral oils in transformers. This study examines the electrical behavior of natural ester-based ZnO nanofluids at different concentrations in the range of 0.05–0.4 g/L. AC breakdown voltages are measured in a horizontally positioned sphere–sphere electrode system according to IEC 60156 specifications. The measurement data are analyzed using Weibull and normal distribution functions. Breakdown voltages with 1%, 10% and 50% probability are also estimated, these probabilities being of great interest for the design of power electrical components. Experimental results show that AC breakdown voltage increases with the concentration of ZnO nanoparticles, except for the concentration of 0.05 and 0.4 g/L of ZnO. Moreover, breakdown voltages at 1% and 10% probability increase by 22.7% and 13.2% when adding 0.1 g/L ZnO to natural ester, respectively.

The electron swarm parameters, namely electron drift velocity, mean energy, effective ionization coefficient and limiting values of number-density-reduced electric fields, E/N, are calculated and assessed in SF₆+CF₄+Ar ternary mixtures for SF₆ concentrations that vary from 1% to 20% over a range of E/N from 50Td to 600Td by solving Boltzmann's equation. The limiting electric field values for the ternary mixtures are deduced from the graphs of the calculated effective ionization coefficients as a function of E/N. Furthermore, breakdown voltage measurements are conducted for the ternary mixtures. The limiting electric field values obtained from the measured breakdown voltages are compared with those of the Boltzmann analysis and found to be in good agreement. The insulation strength of the ternary mixtures with constant Ar concentrations indicated an increase with increasing contents of SF₆ while the share of CF₄ in the mixture reduced in the investigated E/N range up to 600 Td with SF₆ concentrations varying from 1% to 20%. Moreover, a significant synergy is observed due to the non-linear nature of the mixture, and the maximum synergy appears to be around 10% SF₆ in the mixtures of this study with fixed Ar concentration. Furthermore, theoretical calculations of breakdown voltages from Boltzmann analysis are found to be in good correlation with the experimental values.

SF ₆ is a dielectric gas with high dielectric strength which is used in high voltage applications related to power equipment technology. However, its global warming potential (GWP) index and staying time in the atmosphere are very high. In this study, SF6 and its alternatives (tetrafluoromethane (CF4), methane (CH4) and carbon dioxide (CO ₂ )) are investigated with regard to insulation and molecular properties by calculating the distribution of electrostatic potentials using Gaussian 09 and Gauss View 5.0 molecular software programs. The molecular orbital values (homo and lumo), energy gap, hardness, electronegativity, total energy and molecular volume of each gas are obtained by this analysis. It has been found that there is a relationship between the electronegativity and the dielectric strength.

Ultra-dilute SF₆ + N₂ mixtures are subjected to crossed fields with the applied magnetic field normal to the electric field in order to investigate critical magnetic field values for suppression of electron avalanche growth resulting in increased dielectric strength. Electron avalanche growth inhibition together with the related electron mean energy variation and electron energy distribution functions are reported in the binary mixtures subjected to the combined fields. Even if a very small amount of greenhouse gas (SF₆) is used, high dielectric strength can be achieved in the binary mixtures with 0.25%, 0.50%, 0.75%, 3%, and 7% SF₆ contents subjected to the evaluated combined fields. The magnitude of the crossed magnetic field, which results in avalanche growth inhibition, decreases as the electronegativity of the mixture is increased.