Design and installation of extra high voltage cryogenic dielectric test facilities for the superconducting electric equipment

Superconducting electric equipments have a lot of advantages over the conventional devices such as improvements in overall efficiency, size reduction, high current carrying capability, and also environment-friendly products. Owing to these advantages, many research institutes have been tried to develop commercial superconducting devices, which could be applicable to the high voltage and high current electric networks. But up to now, most of the research works to develop commercial products were delayed because it was not easy to acquire reliable high voltage insulation properties and optimum insulation design skills considering extremely low temperature environments. Furthermore, it was difficult to determine optimum high voltage insulation level due to the lack of high voltage cryogenic dielectric test facilities. Thus, in order to establish the cryogenic dielectric technology regarding insulating design, cryogenic dielectric test skills, and to implement more reliable high voltage superconducting devices, high voltage cryogenic dielectric test facilities should be prepared for extra high voltage superconducting electric equipments. Recently, cryogenic dielectric test facilities were installed including 3 m long 2 m wide cryostat system with bushing, and 1.6 MVA lightening impulse generators, 400 kVA AC overvoltage test system in Korea. In this paper, design and installation of high voltage cryogenic dielectric test system including very big size FRP cryostat and high voltage bushing were minutely introduced. And some test results to develop high voltage bushings for liquid nitrogen cryostat in order to implement extra high voltage level bushings were illustrated. These test facilities will be fully utilized for the optimization of insulation design for extra high voltage superconducting electric equipments.