Investigation of partial discharge phenomena in HTS transformer adopting different type of sensors

In this work, we proposed the partial discharge diagnostic techniques to evaluate the cryogenic dielectric insulation of high temperature superconducting (HTS) transformers. Three kinds of different artificial defects were fabricated in order to evaluate partial discharge (PD) characteristics of HTS transformers. Various PD sensors were installed to evaluate the performance of PD detecting characteristics in liquid nitrogen. From the experiments, it was possible to analyze PD signals and to discriminate what kinds of defects exist in cryogenic liquids using various types of PD sensors. Among three PD sensors, AE sensor and HFCT sensor showed more stable performances compared to UHF sensor. But according to the characteristics of defects, three sensors showed different sensitivities according to the PD signal frequency bandwidth of artificial defects. Consequently, this PD measuring technique could be utilized to establish the diagnostic devices for HTS transformer.