Impulsive Breakdown of Mineral Oil and Natural and Synthetic Ester Liquids When Containing Varying Levels of Moisture

This article reports and discusses the results of impulse breakdown study different insulating liquids under highly divergent electric field conditions. Samples a natural ester (Envirotemp FR3), synthetic (MIDEL 7131), naphthenic mineral oil (Shell Diala S4 ZX) at levels relative humidity were exposed to HV impulses with nominal 7- $\mu \text{s}$ rise time 150-kV peak voltage both positive negative polarity. A strong dependence investigated dielectric was observed respect polarity applied impulses. It shown that FR3 liquid has higher strength when than stress. The opposite behavior for MIDEL 7131 Shell ZX which exhibited lower energization as compared energization. prebreakdown obtained in present tests oil, ZX, lie between irrespective been established no statistically significant variations exist parameters (breakdown breakdown) studied their is increased either will help coordination practical applications low environmental impact fluids power pulsed systems components.