The effect of insulating sheets (barriers) in various gaps-the study of AC breakdown voltages and barrier factors

Tests were conducted in order to measure the 60 Hz AC breakdown voltage of small air gaps (up to 0.2 m) formed by an energized and a grounded electrode with a dielectric sheet between them. Energized rod grounded rod and conductor-grounded rod gaps were studied with a flat insulating sheet (barrier) between the electrodes. Qualitative and quantitative results of the test series show how the breakdown voltage varies with the type of electrodes, the distance between the electrodes, the material and size of the barrier, as well as with the relative position of the electrodes and the barrier between them. The maximum flashover voltages occurred when the barriers were positioned at the middle of the rod-rod gap. The maximum flashover voltages were observed when the barrier was at about the 60-90% distance position (i.e. closer to the grounded rod electrode) of the conductor-rod gap.