Streamer Propagation along Profiled Insulator Surfaces under Positive Impulse Voltages

Controlling discharge growth on insulator surfaces is important in high voltage gaseous insulation systems. In this study, the effect of small-scale surface profiles on streamer discharge propagation is examined experimentally. The experimental test objects were 5x72x150 mm polycarbonate plates with and without machined surface profiles. One test object had a surface with 0.5 mm deep semi-circular corrugations, while the other profile had 0.5 mm deep rectangular corrugations. The semi-circular profile increased the surface area with 20 %, while the rectangular profile increased the area with 110 %. A plain surface was also examined as a reference. Positive impulse voltages were applied to a 1 mm thick disk electrode placed 2 mm above the insulator. The insulator was placed in a grounded aluminium casing. The streamer development was imaged with a light-sensitive high-speed camera. Surface charges left on the surface after the impulse were examined using an electrostatic probe and simulations of saturation charge. The rectangular surface profile reduced the streamer range significantly, which suggests an effect of added surface area. Imaging indicated that the wavelike surface streamers follow the profiles closely. Surface potential measurements showed a saddle-shaped distributions, with values in line with saturation charge computations