Characteristics for HVDC GIS/GIL Spacer Under DC Superimposed Lightning Impulse Voltage Conditions

CF3I has excellent insulation performance, arc extinguishing performance, and low GWP characteristics. It is considered as a potential substitute for SF6 in GIS, GIL, circuit breakers, and other high-voltage equipment. In this paper, based on the conservation of charge, heat transfer and partial differential equations (PDE) of ion transport equations, a finite element numerical analysis platform was used to study the evolution of electric field intensity and ion concentration on the surface of the spacer of CF3I/CO2 gas mixture under DC superimposed lightning impulse voltage conditions. The change of the electric field distribution, ion concentration, charge density, and other parameters around the spacer were discussed after the lightning impulse voltage was superimposed, which provided the theoretical basis to the safety, standardization, and design of the future gas insulated systems. The results show that the electric field distribution under DC superimposed positive polarity lightning impulse voltage was the highest, and the positive ions showed an increasing trend while the negative ions showed the opposite trend.