Impact of Shielding on the Gas-Solid Interface Charge Distribution of Real-Sized DC GIS/GIL Insulator

High voltage DC gas insulated switchgear (HVDC GIS) is a crucial part of flexible DC power grid. Under the pressure of DC voltage, the surface charge accumulation of its internal basin insulators is the key problem that affects the insulation performance. In this paper, a surface potential measurement platform for true ±550 kV DC GIS basin insulators was constructed to measure the surface charge of insulators in SF<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> at 0.6 MPa under DC voltage. Based on the experimental results, two modes of charge accumulation are observed: “uniform charge” and “charge speckles”. The uniform charge is regularly and uniformly distributed, and the polarity is the same as that of the applied voltage. The charge speckle is randomly distributed. By introducing a shielding cover, the generation of charge speckles can be reduced, but the basic charge density is increased; the overall charge on the surface of insulator can be significantly reduced by coating on the surface of high voltage electrode and shielding cover. The research on the surface charge accumulation characteristics of the real-sized DC GIS basin insulator and the influence mechanism of key parameters are of great significance to the development and application of DC GIS.