Effect of Temperature-Dependent Volume Conductivity on Surface Charge Accumulation in DC-GIL/GIS

Surface charge accumulation in direct current (DC) gas insulated power line (GIL) and gas insulated switchgear (GIS) is considered a critical issue regarding electrical insulation. Material modification is a useful method to suppress the charge accumulation and promote the insulation property. In this work, a simulation study in 320 kV DC-GIL/GIS was applied under the temperature gradients of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0, 1 5}$</tex>, 30 and 45°C with two materials of different temperature-dependent conductivities to reveal the influence of volume conductivity on surface charging. The simulation results showed that, surface charging was suppressed in terms of saturation time and charge density with the dielectric material of lower volume conductivity. As the temperature gradient increased from 0 to 45°C, the charge density at saturation time increased on the material of lower conductivity, yet it maintained on the material of higher conductivity. The conversion of dominant process of surface charging due to volume conductivity accounted for the distinctions in charge accumulation behaviors for different materials. It deserves more attention on the temperature-dependent characteristics of modified dielectric materials for charge accumulation behaviors and insulation property of insulator in DC-GIL/GIS.