When high-temperature superconducting (HTS) tapes in high voltage DC HTS devices are quenched, amounts of thermal bubbles are generated in liquid nitrogen (LN₂) that will reduce the insulation strength greatly. Especially when resistive-type superconducting fault current limiters meet a short-circuit fault, the insulation strength of the LN₂ decreased significantly due to the thermal bubbles and electrothermal pressure. Solid insulating barriers can improve the insulation strength of the LN₂. The objective of this study is to obtain the effect of barrier thickness on the DC dielectric breakdown characteristics of LN₂. Insulating barrier Polytetrafluoroethylene with three different thicknesses were tested. Three types of electrodes such as rod-plane, needle-plane, and plane-plane were applied. The results showed that the barriers can increase the negative and positive breakdown voltage both with and without thermal bubbles in a slightly non-uniform field (SNF) and non-uniform field (NF). For the SNF, the DC breakdown voltage is higher when the barrier is thinner. The effect of the barrier thickness in the NF is lower than that in the SNF field. For the NF, the positive breakdown voltage is higher when the barrier is thicker.

中文翻译：

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聚四氟乙烯阻挡层厚度对液氮直流击穿特性的影响

当高压直流 HTS 器件中的高温超导 (HTS) 带淬火时，液氮 (LN ₂ ) 中会产生大量热气泡，这将大大降低绝缘强度。尤其是电阻型超导故障限流器遇到短路故障时，由于热气泡和电热压力的作用，LN ₂的绝缘强度明显下降。固体绝缘屏障可以提高LN ₂的绝缘强度。本研究的目的是获得势垒厚度对 LN _{2直流介质击穿特性的影响。}. 测试了三种不同厚度的绝缘屏障聚四氟乙烯。应用了三种类型的电极，例如棒平面、针平面和平面平面。结果表明，在轻微非均匀场（SNF）和非均匀场（NF）中，无论有无热气泡，势垒都能增加负和正击穿电压。对于 SNF，势垒越薄，直流击穿电压越高。NF中势垒厚度的影响低于SNF场。对于 NF，势垒越厚，正击穿电压越高。