The study of flashover characteristics of insulating materials on different conditions is of importance to obtaining the electrical strength of insulators and ensuring the safety of electrical equipment. Therefore

a series of surface discharge electrodes with different electric fields was developed

and then the insulating performances of epoxy resin in vacuum and air were experimentally studied under DC voltage. Furthermore

the flashover voltage obtained from experiments was analyzed using the Weibull distribution. Results show that the flashover voltage under highly uneven field is lower than that under slightly uneven field. The randomness of discharge channel and flashover voltage in vacuum is greater than that in air

and vacuum flashover is impacted by the solid dielectric more significantly than that in air. Under asymmetric electric field

the flashover voltage has a polarity effect

and the effect in vacuum is opposite to that in air. In addition

the DC flashover voltage of epoxy resin obeys the Weibull distribution

which can be used to assess the sensitivity of insulating systems to the applied voltage quantitatively. The introduction of the location parameter can improve the data fitting results

and the characteristic flashover voltage and flashover voltage with 0.1% flashover probability further improve the evaluation method of the electrical performances of insulating materials.