Bubble deformation in the repetitive pulsed glycerin pulse forming line and its relation with the liquid breakdown

Abstract

Glycerin is a promising liquid dielectric for pulsed power systems because of its high storage energy density and high resistivity. In order to further improve the energy storage density of glycerin, its breakdown characteristics should be investigated. In this paper, experiments are carried out to study the decline of the breakdown voltage of glycerin in a repetitive pulsed pulse forming line (PFL) in both the single pulse mode and the repetitive pulsed mode. It is shown that the breakdown voltage of the glycerin PFL is reduced by about 35% after 100 pulses in 10 s. The bubbles in glycerin are suspected to be an important factor affecting the breakdown characteristics. By using a high-speed camera, the deformation of bubbles (especially the height) is observed in the experiments and the deformation of bubbles is cumulative after multiple pulses. Experiments confirm that the bubbles' height is influenced by factors including the electric field, pressure, and temperature. These experimental results demonstrate an important process of the liquid breakdown in the repetitive pulsed mode, which will be helpful to improve the breakdown characteristics of liquid dielectrics.