Influence of insulation barrier on AC flashover voltage with and without grounded back electrode in air

The grounded back electrode can reduce the breakdown voltage. Inserting an insulation barrier is an effective way to increase breakdown voltage. The objective of this paper is to investigate the impact of barrier on AC breakdown with back electrode. The breakdown voltage is acquired from the experiments. The electric field distribution at breakdown is also obtained via software simulation. The experiments and analysis for both `with´ and `without´ back electrode are performed. From the results, the barrier can effectively increase breakdown voltage, especially for the case with back electrode. Without back electrode, there is only one breakdown trajectory path. The breakdown trajectory is very similar for all breakdown cases without back electrode. However, with back electrode, there are three breakdown trajectory patterns in total. The behaviors of breakdown voltage and electric field vary between different patterns. The analysis indicates that electric field distribution controls breakdown characteristics. The partial discharge (PD) streamers and residual charge induced by the electric field is the key to explain all the phenomena.