Testing and long term performance of gas-insulated DC compact switchgear

Compact gas-insulated systems for HVDC applications are under development worldwide. Insulation requirements and adequate testing procedures are not yet fixed as standards. Only limited long term experience is available today. For DC compact switchgear (DCCS) several physical mechanisms, like accumulation of electric charges and temperature-dependent conductivities, have to be considered. Time-dependent charge accumulation in and on insulators occurs under DC voltage stress, influenced by the insulator geometry and its material, with field transition within minutes to months. Further, the nonlinear material properties and their interdependencies bring up some challenges. This paper gives an overview of appropriate testing procedures for DCCS, based on AC standards and complemented by…