Influence of Support Insulators on the AC Electrical Strength of Parallel-Cylindrical Conductors in Liquid Nitrogen

In order to make superconducting high-voltage power cables more compact and easier to manufacture, it may be possible to dispense with solid electrical insulation and use liquid nitrogen (LN
2
) instead. LN
2
has very good electrical properties. However, each phase conductor of a three-phase, LN
2
-insulated arrangement of such a cable must be kept at a distance from each other and from the surrounding earthed cryostat by means of a support insulator. In this work it is therefore investigated what influence different insulating materials have on the electrical strength. For this purpose, a simple straight model insulator of a support insulator was developed and manufactured from the materials PTFE, PP, PE, POM-C, and twice GRP and tested for their electrical flashover properties. In comparison to the breakdown properties of LN
2
in the same test arrangement, most materials surprisingly showed the same or only slightly reduced electrical flashover strength. PE shows the best properties on average, followed by POM-C, PP, GRP EGS 102 and PTFE. The highest average reduction in electrical strength, at almost 26%, is caused by GRP G11.