Conceptual Design of Current Leads for 154 kV SFCLs

Study of the dielectric characteristics on gaseous insulation media is important for designing and developing current leads of superconducting machines with a sub-cooled cooling method. In the case of using a sub-cooled N₂ cooling method, a gaseous insulation medium, such as He, Ne, SF₆, CF₄, or N₂, should be injected to control the pressure and enhance the dielectric performance of current leads simultaneously. In this study, dielectric experiments on various gaseous insulation media are conducted and experimental results are analysed by considering field utilization factors. In addition, the functional equations are derived from experimental results and computational analyses. It is found that the dielectric characteristics of gaseous insulation media are determined by the maximum electric field intensity at sparkover voltage. This denotes that the electrical breakdown voltage of insulation gas could be estimated using deduced functional equations. Finally, the conceptual electrical insulation designs of current leads for a superconducting apparatus according to various insulation media are presented and the results are compared. The results may be applied to develop and commercialize a high voltage superconducting apparatus using a sub-cooled N₂ cooling method.