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Description
A study on the cryogenic dielectric characteristics for developing a high voltage superconducting magnet system such as a superconducting fault current limiter, a superconducting transformer, and a superconducting cable has been performed. A high voltage superconducting magnet system uses liquid nitrogen as an insulating medium as well as a cooling medium by immersing a superconducting magnet into liquid nitrogen and uses gaseous nitrogen as an insulating medium by pressurizing. In many cases, electrical breakdown occurs frequently where a current lead and an enclosure meet due to the vulnerable dielectric characteristics of gaseous nitrogen compared with those of liquid nitrogen. In this study, the dielectric characteristics of gaseous nitrogen according to the work function of materials is performed and a new method for enhancing the dielectric characteristics of a high voltage superconducting magnet system is proposed. As a result, it is found that the probability of electrical breakdown at the dielectric weak point of a high voltage superconducting magnet system could be enhanced by adopting the proposed method.
