High voltage insulation test for high Tc superconducting types

The development of high T_c superconductors (HTS) has now reached the stage where their application in power system equipment is in the process of being implemented. As a consequence there is a need to investigate the properties and applicability of high voltage insulation at cryogenic temperatures. This paper will examine the insulating materials being used at such temperatures and the dielectric properties of such materials. A major factor in the deterioration of electrical insulation at normal operating conditions is the insulation temperature and there is a well developed understanding of the aging characteristics under such temperature conditions. However, at cryogenic temperatures the properties of insulation under high electric stress may be quite different than the case for conventional operating temperatures and the aging process may be substantially altered. There is thus a need to investigate the insulation properties at cryogenic temperatures. This paper reviews the test methods for condition monitoring of insulation under such conditions and reports the first part of experimental results at ambient condition. The results obtained and further study at cryogenic temperature will provide necessary information for design of new HTS equipment.