High-voltage design optimization requires a fun- damental understanding of electrical breakdown mechanisms under different stress situations. The impulse withstand voltage is normally used as dimensioning criterion for medium voltage air-insulated systems as flashover mechanisms in air are rapid. Prediction of withstand voltage relies on streamer inception and propagation models that are not always sufficiently accurate. Positive impulse voltage experiments were performed on a rod- plane gap with a dielectric barrier at different positions parallel to the ground plane. Streamers initiate from the rod tip and propagate in the field direction. Charge deposited on the dielectric surface changes the field situation and can result in a higher inception voltage. The streamer propagation was recorded with a fast ICCD camera. Finite element method field simulations of the background field were used to evaluate the effect of a barrier surface potential on the streamer inception voltage. Streamers reach the ground electrode without initiating electrical breakdown. The discharge activity from the rod was reduced by deposited charge on the barrier.
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