절연파괴에 따른 2세대 고온 초전도선재의 열화특성에 관한 연구

Abstract

2G high temperature superconducting (HTS) wires have been widely adopted to develop high voltage superconducting apparatuses such as a superconducting fault current limiter (SFCL), a superconducting cable, a superconducting transformer, and so on. A study on the dielectric degradation characteristics of 2G HTS wires due to electrical breakdown should be performed to enhance the stability and to accelerate the commercialization of high voltage superconducting apparatuses. In this study, the degradation characteristics of 2G HTS wires, SCN-04 made by SuNAM Co., Ltd. are analyzed by dielectric experiments with AC and lightning impulse voltage in saturated liquid nitrogen (LN2) of 77K. The 2G HTS wire used in this study has silver stabilizing layers on both sides of GdBCO layer. Also, the substrate is made with stainless steel and whole 2G HTS wire is surrounded by copper. It is verified that the degree of degradation of the 2G HTS wire is affected by the magnitude of the applied voltage and the type of voltage. Also, cracked GdBCO layer due to electrical breakdown is shown by scanning electron microscope (SEM) image. The degradation characteristics such as critical current and index n of 2G HTS wire due to electrical breakdown can be explained by mechanical cracked structure of a GdBCO layer.