Simulation Study of External Coil on Discharge Characteristics of Liquid Nitrogen Switch Under Multi-Electrode Conditions

Sulfur hexafluoride(SF
₆
) is widely used in high-voltage transmission and distribution equipment in the power industry due to its excellent arc extinguishing and insulating ability, but it is prone to produce toxic gases at high temperatures and causing the greenhouse effect due to arc discharge and other behaviors. Due to its good insulating properties, liquid nitrogen(LN
₂
) is considered an effective alternative to SF
₆
and is being used in new power switchgear. For the design of new power switchgear, it is very important to select suitable electrodes and reduce generation of nitrogen during the discharge process. In this work, multiphysics field simulation software simulated the electric field strength of a metal-enclosed LN
₂
switch under different electrode conditions. The results show that the plate electrode's electric field is symmetrically distributed on both sides of the pole plate, the plate-rod electrode, the higher value of the electric field intensity is concentrated at the tip of the rod electrode, and the value of the electric field intensity is smaller in stainless steel under a large gap. Interference from external coils at large electrode gaps is one of the main causes of temperature variations in LN
₂
. Symmetrical plate-plate electrodes usually have lower temperatures than plate-rod electrodes, and stainless steel materials further reduce the temperature in LN
₂
. However, the localized high temperatures on the surface of the electrodes due to the discharge make them more susceptible to surface damage than copper.