Simulation Study on Discharge Characteristics of Metal-Enclosed Liquid Nitrogen Switch

Sulfur hexafluoride(SF 6 ) is widely used in high-voltage circuit breakers due to its excellent insulation capability. At high temperatures, SF 6 tends to break down and produce toxic gases, which exacerbates the greenhouse impact. Given its excellent insulating qualities and environmental friendliness, liquid nitrogen(LN 2 ) has the potential to replace other insulating materials in circuit breakers in the future. In this paper, metal-enclosed LN 2 switching discharge characteristics are simulated by altering three conditions: electrode shape, electrode material, and LN 2 temperature. The experiments were conducted using DC and various electrode spacings based on local thermodynamic equilibrium(LTE), and eventually changes in potential and pressure inside the closed cavity were noticed. The experimental results found that the sphere symmetric electrode has the lowest potential mean value at the small gap, meanwhile, the rod-sphere electrode has the lowest electric potential mean value at the large gap. In addition, the average value of pressure inside the chamber using the rod electrode was the lowest. The average rate of change of simulated electric potential and pressure was always the lowest using electrodes made of stainless steel.