Small air gap’s performance under non-uniform electrical field with silicone tubular barriers under AC voltage

The objective is to compare the electrical performance of a tubular barrier made of silicone and glass protecting an air gap with an alternating electric field. This investigation is focused on rod–rod and rod–plane electrode systems with variable interelectrode distance. An experimental device consists of wooden support in U shape. The air space disruption tests of the two systems with tubular barriers were supported by a visualization of the path of their electrical rupture. A disruption model of a non-uniform electric field air gap was developed in this study. Using the experimental results of dielectric breakdown of the considered systems, this model characterizes the flashover voltage as a function of the barrier insulation’s nature. In addition, it allows an easy comparison of its electrical insulation capacity under these conditions. Under pollution, no protection is provided by a glass barrier to the two systems due to the highly conductive behaviour of the pollution layer covering its surface. On the other hand, that offered by a tubular silicone barrier is by far the best because of the flashover discharge’s presence on its surface under these conditions. In a clean and dry atmosphere, the electrical insulation power of the systems is more efficient with a silicone barrier than with a glass one, because of its more advantageous dielectric properties and its lightness.