Study on the Breakdown Voltage Characterization of Insulation Gases for Developing a High Voltage Superconducting Apparatus

A sub-cooled liquid nitrogen system is known to be a promising method to develop a high voltage superconducting magnet. Therefore, the investigation of dielectric characteristics of gaseous electrical insulation media is important for the design of a high voltage superconducting apparatus. In this paper, dielectric characteristics of various gases according to utilization factors are investigated for the establishment of insulation design criteria of a high voltage superconducting apparatus. Dielectric experiments on gaseous nitrogen and gaseous helium (GHe) are carried out by using several kinds of sphere-to-plane electrode systems made of stainless steel. As a result, it is found that the dielectric characteristics of gas are determined by as well as gap length of electrode systems. Also, empirical expressions for electrical breakdown performance of gaseous electrical insulation media are derived and formulated. It is considered that the results of the study would be applicable to designing a high voltage superconducting apparatus.