Specifications and performance experiences of internally cooled small-scale SMES

Abstract SMES has a high potential for application in power utility, because of high plant efficiency, quick response, and power controllability. SMES is composed of a superconducting coil, vapor-cooled leads, and a power conditioning system. The electrical specifications for SMES are discussed on the basis of input and output power depending on size and application. As breakdown voltage in helium gas is low, an internally cooled magnet system is preferable to a pool boiling one. A model coil for a 100 kWh SMES, which is a typical forced cooled magnet system, was developed in Japan and then successfully tested. A glass–polyimide–glass tape insulation system was investigated in view of electrical and mechanical strength prior to fabrication. The breakdown voltage measurement of a sample with an artificial crack showed sufficient strength. The insulation critical fracture strength has a good agreement with the Mohr–Coulomb criterion.