Analysis on the Dielectric Characteristics of Insulation Gases for Developing a High Voltage Superconducting Fault Current Limiter

A sub-cooled liquid nitrogen (LN₂) cooling system is known as an appropriate method for developing a high voltage superconducting fault current limiter (SFCL). The pressure of a sub-cooled LN₂ cooling system should be controlled by injecting non-condensable gas such as gaseous helium (GHe) and gaseous neon (GNe) into the cryostat. Therefore, the electrical breakdown voltage of current leads is directly influenced by an injected gaseous medium. In this study, electrical insulation experiments on GHe and GNe are conducted and the results are compared with each other. Also, the dielectric characteristics of GHe and GNe are analyzed by using field utilization factors. It is found that the dielectric characteristics of GHe are superior to those of GNe under the same conditions. The experimental results are applicable for designing the current leads of a high voltage superconducting fault current limiter.