Dielectric measurements on cryogenic insulation systems

For the operation of high temperature superconducting (HTS) devices liquid nitrogen (LN2) is necessary to cool the HTS conductor down to the operating temperature of about 77 K. Depending on the application in electrical power systems and high voltage devices, LN2 is also an attractive dielectric liquid. Some prototypes of cables, power and traction transformers and current limiters were built, but there is not sufficient knowledge about optimum dielectric structures and ageing. The aim for the measurements is to test different electrical insulating structures in specified LN2 at AC, DC and impulse voltages and to observe the partial discharge behaviour, breakdown voltage and ageing.