Research on the suppression of bubble in liquid-solid composite insulation and the improvement of voltage endurance.

关于气泡对低温液体绝缘电击穿的影响，有气泡液氮的电强度为无气泡液体与蒸汽的平均值，且随着气泡的增大而减小。用气泡对薄弱点分布的体积理论对其进行了解释。观察了气泡在高电场中的表现。液氮中的气泡向电场方向拉伸变形，在电极之间架起桥梁，气泡内放电。比较了在液氦和液氮中局部放电对复合材料绝缘的降解。实验研究了真空局部放电降解和复合绝缘的层效应。最后提出了一种新型的抑制气泡的液固复合保温系统，并用模型保温系统进行了实验验证。其思路是将低温液体的冷却剂与无液体的固体绝缘分离。

About the effect of bubble on the electric breakdown of cryogenic liquid insulation, the electric strength of liquid nitrogen with bubble was the average value of them between the liquid without bubble and the vapor, and reduced with the increase of bubble. It was explained by the volume theory on the distribution of weak points by bubbles. The performance of bubble in the high electric field was observed. The bubble in liquid nitrogen was deformed by stretching to the direction of field and made a bridge between electrodes with internal discharge in bubble. The degradation of composite insulation by partial discharge in liquid helium was compared it in liquid nitrogen. The degradaftion by partial discharge in void and the layer effect in composite insulation was studied experimentally. Finally the new insulation system with suppression of bubble in liquid-solid composite insulation was proposed and tested experimentally with model insulation system. The idea is to separate the coolant of cryogenic liquid inside hollow conductor with insulation of solid without liquid.