Experimental study on surface flashover of PMMA and SR driven by negative DC voltage at atmospheric pressure

Silicone rubber (SR) and polymethylmethacrylate (PMMA) are widely used as insulators. To ensure the safe and stable operation of electrical equipment, it is very necessary to study the flashover performance of insulating materials. In this paper, the surface flashover characteristics of SR and PMMA under atmospheric pressure were studied by using the bar-bar electrode and pin-pin electrode, which were driven by the negative DC power supply. The experimental results indicate that the flashover voltage of PMMA with low dielectric constant is higher and the flashover voltage of the two kinds of materials both obeys the two-parameter Webb distribution. It is found that the parameter α under highly non-uniform filed is lower than that under slightly non-uniform filed, while the variation tendency of β is opposite. Besides, a method to calculate the probability of surface flashover is provided. The average flashover electric field strength of the slightly non-uniform filed is larger while the maximum flashover electric field strength of the highly non-uniform filed is larger. This paper provides some reference for the study of the insulation characteristics of different materials and the insulation design of the system.