How Temperature and Pressure Affect the Electric Field Distribution in HVDC GIS/GIL: A Numerical Study

In this paper, an electro-thermal based surface charge accumulation model is established. Heat conduction, heat convection and heat radiation are included. The gas flow is coupled with fluid equations to describe the motion of charge carriers, and gas current density is also corrected by the gas velocity. In terms of it, the surface charge and electric field on a basin-type insulator in vertical laid DC gas insulated switchgear (GIS) and gas insulated transmission line (GIL) under different temperatures and pressures are studied. The results show that a temperature gradient is formed in the gas from top to bottom in the vertical direction, and the increase in pressure leads to a higher temperature of the lower surface. The surface charge density and tangential electric field increase with the temperature and decrease with the pressure. As a comparison, the surface charge and tangential electric field are calculated without considering temperature and without considering heat convection. The former leads to a lower tangential electric field than this model, while the latter brings about a higher electric field. This paper provides a more accurate reference for the design of DC GIS/GIL through a more comprehensive model.