Dielectric Tests of Superconducting Coils for Development of High Voltage Superconducting Machines

This paper deals with the dielectric breakdown characteristics of superconducting coils for development of high voltage superconducting machines such as superconducting fault current limiter (SFCL) and superconducting transformer. The electrode systems are simulated to investigate the dielectric breakdown characteristics of solenoid and pancake coil. Dielectric breakdown tests are carried out on several basic electrode systems: needle-plane, sphere-plane, rod-plane, cutting bar-plane, and rounded bar-plane electrodes. These results could be applied to design the high voltage superconducting magnet system. Dielectric tests of turn-turn and layer-layer in solenoid coil are performed according to the groove depth, pitch length, and the distance between two layers. Dielectric tests of turn-turn with various insulation materials are also performed in pancake coil. In addition, the deterioration of high temperature superconducting (HTS) tapes and coils due to the electrical breakdown are investigated experimentally. It is proven that the HTS tape and coil could be robust to the electrical breakdown by the laminated metal.