Surface charging of dielectric barriers in short rod-plane air gaps – experiments and simulations
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Surface charge on dielectric surfaces can alter the field conditions of insulation systems substantially. In this work, lightning impulse experiments are compared with a simulation model for surface charging in rod-barrier-plane geometries. The model is based on the saturation charge assumption, i.e. zero normal electric field in air pointing onto the dielectric surface, which prevents further charging. This hypothesis holds well for most geometries, as long as there are no leader discharges or restrikes (also known as back discharges). Restrikes are discharges that occur on the lightning impulse tail when the active electrode is close to zero potential. A method is proposed to compute the charge distribution after a restrike. Furthermore, the model can predict discharges on both sides of the barrier. Saturation charge fields can be computed efficiently, so the results are encouraging for dielectric design applications.