Cryogenic Benefits of a 70 kA High Temperature Superconductor Current Lead

A 70 kA high temperature superconductor current lead (HTS‐CL) was developed, built partly together with industry and tested at this current level at the Forschungszentrum Karlsruhe in 2004 and 2005. The HTS‐CL consists of three main parts, the cold end for the connection to the bus bar at 4.5 K, the HTS part operating in the temperature range from 4.5 K to 65 K and a copper heat exchanger (HEX) in the temperature range from 65 K to room temperature. The lead was designed for a He inlet temperature to the HEX of 50 K but was also tested with a He inlet temperature of 4.5 K and 80 K. In a further step, a test with direct LN2 cooling with and without sub‐atmospheric pressure operation was successfully performed up to a current of 75 kA.The operation at a temperature level above 4.5 K reduces the required power consumption of the cryoplant by a factor of 1.3 in case of 80 K He inlet temperature and up to a factor of 3.0 for 50 K He and direct LN2 cooling. Details of these operation modes including the advantages of the cryogenic system will be outlined.