Abstract

A resistive-type superconducting fault current limiter (SFCL) is one of the most promising superconducting devices in an electrical power system. However, an SFCL has the very obvious disadvantage of a large space requirement when applied in high-voltage-level power networks. Considering the space utilization efficiency, a pancake structure in which superconducting tapes are wound into coils should be adopted. When certain faults occur in a power grid, a relatively high voltage difference will be present in the tape coil. The inner and outer layers are in direct contact; therefore, special measures have to be carried out to overcome high-voltage insulation safety issues. Two commonly used materials are considered in this study: Nomex and Kapton. The basic AC breakdown characteristics in air and liquid nitrogen are explored. A new breakdown-strength testing platform is manufactured to obtain the breakdown voltage. Considering that the edges of the superconducting tape are very thin, the impact of the superconducting-tape thickness on the breakdown strength is explored. Two methods, parallel and vertical lapping, are used to lap the insulation layer onto the tape and are subsequently compared. Finally, a face-to-face electrode structure breakdown test is conducted to simulate the actual working conditions in a tape coil. The results obtained can be used to design and optimize the geometrical structure of the SFCL pancake component.

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