Dielectric strength of superconducting tape arrangements in liquid nitrogen

Superconducting devices, in particular cables and current limiters based on high-temperature superconductors (HTS) and cooled with liquid nitrogen (LN2) at 77 K, are available on the market for medium-voltage applications. However, only a few prototypes of superconducting devices have so far been built for the high-voltage levels from 123 kV. In order to optimize superconducting devices with regard to its compactness, the properties of the electrical insulation systems must be investigated and improved in detail. Therefore, the dielectric strength of arrangements of superconducting tapes in LN2 was investigated as a function of the overall dimensions and the microscopic edge geometries of various tape conductors and compared with strength values of tip-plane arrangements. The results show that the microscopic edge geometries of the individual tape conductors have a negligible influence on the breakdown behaviour. Instead, the conductors height appears to be the determining factor for the expected dielectric strength of the arrangement.