Insulation Systems for Superconducting Power Devices: Normal Operation Versus Abnormal Conditions
Application of superconductivity in electrical power systems has been a fascinating option since the early sixties. The high current capacity of superconductors was claimed in an euphoric manner to open a way for improved devices with huge power ratings; prototypes for transmission lines with cold dielectric, exciter rotors for generators, Superconducting Magnetic Energy Storage (SMES) as well as model magnets for future fusion reactors, have been successfully built and operated1. Liquid or Supercritical Helium (LHe, SHe), respectively, was indispensable to cool the classical metallic superconductors with very low critical temperature, and cold helium performed also well as an insulating fluid up to more than 500 kV test voltages, notwithstanding many Cassandra Cries based on the known dielectric weakness of helium gas at ambient conditions. There is now undoubted some confidence on reliable voltage insulation at low temperatures.
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