Abstract
The insulator in direct current gas-insulated transmission lines (DC-GIL) would suffer discharge risk due to surface charge accumulation under thermal-electric coupled fields. In this paper, the transient surface charge accumulation characteristics of a basin-type DC-GIL insulator is investigated via finite element method based on a three-dimension horizontally installed GIL model. The stationary temperature distribution of the model is obtained and then applied to the transient simulation of charge. Weak form partial differential equation is employed to deal with the ion transportation equation. Equations and parameters in the simulation are optimized to reduce the computing memory and time. Results indicate that the charge accumulation is accelerated due to the promotion of conduction through the insulator under thermal gradient. Higher charge density is obtained under thermal gradient. And the surface charge density of the convex surface is higher due to the promoted conduction. The highest field strength increases and the corresponding location moves along the convex surface during the transient process. This could attribute to the influence of transient charge behavior under thermal gradient on the electric field distribution. This study indicates that the thermal gradient and transient charge accumulation should be considered when dealing with the insulation characteristics of DC-GIL with insulators.
Highlights
Gas-insulated transmission lines (GIL) and gas-insulated switchgear (GIS) are widely applied in power systems due to the advantages of space-saving, easy maintenance, large capacity, and high reliability [1]
Since spatial distributed thermal gradient is established in the pipe and the insulator, and 3D geometry model is needed in the simulation
Weak form partial differential equation (PDE) was applied to deal with the ion transport equation in the simulation of charge
Summary
Gas-insulated transmission lines (GIL) and gas-insulated switchgear (GIS) are widely applied in power systems due to the advantages of space-saving, easy maintenance, large capacity, and high reliability [1]. It was found that the electric conductivity of the insulator would affect the surface charge distribution characteristics [12], [13] This thermal gradient should be involved when dealing with the electric field property of the insulator under DC stress considering the temperature-dependent electric conductivity of the insulator [14]. The surface charge distribution of the insulator in 3D mode can’t be obtained This leads to the impossibility of the investigation in some conditions, for example, the horizontally installed GIS/GILs. Since spatial distributed thermal gradient is established in the pipe and the insulator, and 3D geometry model is needed in the simulation. This work can be beneficial to evaluate the insulation property of DCGIS/GILs during long-term operation
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