Barrier Position Effect on Bubble Triggered DC Breakdown Characteristics in Liquid Nitrogen

The objective of this study is to determine the effect of different barrier positions on the DC breakdown characteristics of liquid nitrogen (LN2), with and without bubbles. The DC breakdown voltage is measured of a needle-to-plane electrode, with 9 mm gap distance, with and without PTFE barrier insulation of 40 mu m thickness. The presence of bubbles lowers the breakdown voltage and the effect of have the barrier at various distances from the tip of the needle electrode is studied. The results show that with and without bubbles, the closer the barrier to the needle electrode, the higher the breakdown voltage. Observations using a high-speed camera show that the presence of the insulation barrier triggers the breakdown of the LN2/insulation barrier composite system.