Development of 2 kA high-temperature-superconductor current lead system for AC applications

High-temperature-superconductor (HTS) current leads are suitable for AC applications because of lower AC loss during operation as well as their lower thermal conductivity. We have designed, fabricated and tested a 2 kA HTS current lead system. It is composed of copper leads for the higher temperature region and HTS elements (BSCCO-2223) for the lower temperature region. The copper section is cooled with cold nitrogen gas, while the HTS section is cooled by solid state heat conduction. Tests demonstrated the current lead system can successfully conduct a current of 2000 Arms at 50 Hz. In order to investigate to evaluate the performance of the current lead system, measurements such as the steady state hop-off rate of cooling gas at various operating currents and the characteristics of current sharing in each HTS element were made. Tests of a.c. behavior in HTS elements were also carried out.