Simulation study on surface charge distribution characteristics of surface discharges in air

The surface charge accumulated on insulating materials could distort the electric field along dielectric surfaces and further cause flashover. In order to study the dynamic charge accumulation on a dielectric surface in the air during the discharge，chemical reactions were added to a 2D fluid model for surface discharge simulations，and then the surface charge evolution during discharge inception，attachment to the dielectric and propagation over the surface were simulated for cases which positive and negative voltages are applied，respectively. We found that when the applied voltage is negative，the accumulated charges are always negative. The peak value is around the streamer head for a surface streamer；the polarity of the electric field at the interface would reverse when the streamer head passed by，then positive ions would move to the surface. When the applied voltage is positive，positive charges are ac⁃ cumulated at the head of the surface streamer，and at the streamer tail electrons diffuse toward the surface，and the to⁃ tal charge on the dielectric surface turns negative.