DC Superconducting Cable Using $\hbox {MgB}_{2}$ Wires

Tsinghua University, University of Cambridge, and MIT are collaborating to design, construct, and test an MgB₂ dc cable for microgrid applications. Two-stage current leads with nitrogen vapor cooled copper and gaseous helium cooled hightemperature superconductor will be used. The two-stage cryostat will be cooled using a single helium fan with a recuperator. The helium gas used to cool the MgB₂ to 20-25 K will be cooled with a two-stage GM cryocooler. The cryogenic stability of the cable will be presented. Designs of cryostats are being investigated. Semi-rigid cryostats, with low heat leak, are being designed and will be tested as part of this program. The system will operate up to 1 kV and 1 kA, limited by the present power equipment. However, the MgB₂ conductor is being designed for 5 kA, and may be tested at low voltage with upgraded current leads. A 30-m cable will be tested using facilities at Tsinghua University in Beijing.