Partial Discharge Measurements of Cryogenic Dielectric Materials in an HTS Transformer Using HFCT

Various types of high-temperature superconducting (HTS) devices have been developed, some of which have completed field testing and are ready for use in commercial applications. In order to facilitate the commercialization of HTS electric equipment for extra high voltage levels, cryogenic dielectric technologies should be established. In this work, in order to develop partial discharge (PD) measurement techniques for HTS transformers, artificial defects were installed both in liquid nitrogen and insulating oil. Experimental investigations were carried out for the diagnosis of the HTS transformer, and various PD patterns, which occurred due to the artificial defects of immersion in both insulating oil and liquid nitrogen, were measured. Throughout this work, the PD patterns that occurred in liquid nitrogen were detected, analyzed, and compared to those in insulating oil through the use of a high frequency current transformer (HFCT) diagnostic method. The partial discharge measuring techniques we developed could be fundamental in establishing HTS transformer diagnosis technologies for power applications.