Solid-gas interfaces in DC gas insulated systems

Inhalt:
This contribution presents a model that is appropriate for the simulation of field distributions and surface charge accumulation in a DC GIS environment. The dimensioning of HVDC GIS requires understanding of all relevant charge transport processes in the gas as well as in the solid insulation. Moreover, physical processes at the various interfaces are crucial, as in most cases dielectric failure occurs in the gas near solid surfaces and is often mediated by surface charges. Furthermore, temperature gradients in the insulation lead to large conductivity gradients and by this strong distortion of the DC field distribution, which necessitates the consideration of heat fluxes (conduction, radiation and convection) from the hot conductor to the colder outer enclosure. This model is used for the optimization of insulation geometry and insulation materials. It also allows checking the robustness of the insulation with respect to various GIS geometrical configurations and orientations, as well as all needed operation conditions.