Design and test results of 66 kV high-Tc superconducting fault current limiter magnet

This paper describes the design of a 66 kV high-Tc superconducting fault current limiter (FCL) magnet and the test results obtained. The magnet mainly consists of a vacuum vessel, a nitrogen bath, a pair of current leads, cryocoolers, and six sets of coils wound with Bi2223 tape. The rated current is 750 A. The insulation voltage of the magnet is of the 66 kV class. In the final year of the project, all six sets of the coils are set connected in the cryostat and evaluation tests have been implemented. In the,cooling test, sub-cooled nitrogen of 65 K was obtained, with homogenous temperature distribution in the cryogen. The rated current of 750 A was successfully obtained for both direct and alternating current tests. In addition, the magnet passed the simultaneous current and voltage application test. The dielectric test results showed that the magnet satisfied the insulation for 66 kV apparatus in the Japanese Electrotechnical Committee Standard. Finally, the magnet was combined with a rectifier bridge circuit to form an FCL. In a fault current limiting test with a short-circuit generator, the FCL successfully limited short circuit current up to 20 kV applied voltage. The obtained result was in good agreement with the design and the Electro-Magnetic Transients Program (EMTP) analysis.