Interaction and Start-up Dynamics Analysis of Metallic Dust in GIS under DC Voltage

Gas-insulated switchgear (GIS) inevitably contains metal dust. The start-up and migration of metallic dust under an electric field are critical factors in initiating insulation failure. This paper develops a dust start-up dynamic model considering interaction forces, analyzes the dynamic mechanisms of dust start-up, investigates the effects of accumulation form, material, and particle size on the start-up behavior, and explores the special agglomeration phenomenon during the dust start-up process. The results show that the dust start-up is divided into two stages: in the initial stage of start-up, dust exhibits a point-like distribution in the gas gap. At the large-scale start-up stage, dust forms elongated, diffuse bands that span the gas gap, leading to a substantial decrease in the insulation margin. The value of Coulomb force between dust is comparable to that of electric field force, and Van der Waals forces have a significant effect on the start-up behavior. For 1200 mesh aluminum dust, the errors between the simulated and experimental values are 62.5% and 63.8%, for the initial start-up voltage and large-scale start-up voltage, respectively, when Van der Waals forces are neglected. After considering the van der Waals forces, the errors are reduced to 7.47% and 6.04%. For aluminum powder, start-up is more likely to occur when the particle size is in the ranges of 5000–10000 mesh and 180–250 mesh, posing a greater potential threat to equipment insulation performance. In addition, the phenomenon of “dust agglomerate” start-up was observed. When the “dust agglomerate” moves to the high-voltage conductor, it collides and pulverizes, posing a potential risk to the equipment. This work provides data support and a theoretical foundation for metal dust suppression in GIS, and the special phenomenon of "dust agglomerate" found can provide new ideas for improving the reliability of GIS.