Experimental investigation on the role of electrodes in solid dielectric breakdown under nanosecond pulses

Based on a nanosecond-pulse generator and dozens of polyethylene samples, the role of electrodes in dielectric breakdown under nanosecond pulses is experimentally investigated. The test factors include electrode material, electrode configuration, and pulse polarity. For the electrode material effect, metals of copper, stainless steel, aluminum, and tungsten are manufactured and investigated. The experimental results show that the larger the work function of the metal, the greater the electric breakdown strength (E_BD). For the electrode configuration effect, electrodes with radius of 1 mm and 30 mm are respectively employed. By comparing the relevant experimental results, it is found that the smaller the radius of the electrode, the larger the E_BD. The experimental results on pulse polarity show that there is a `weak´ pulse polarity effect for the breakdown of PE, and the ratio of E_BD under positive pulses to that under negative pulses is 0.8-0.9. All the experimental results reveal that the electrode plays a role of generating seed electrons/holes in dielectric breakdown in nanosecond time scale. In addition, based on the experimental results, a mechanism for solid dielectric breakdown under nanosecond pulses is also proposed in this paper.