Restrain effect of partial discharge spreading by insulator surface barriers

We have made researches on the internal partial discharge degradation phenomena of dielectric materials. In this paper, we investigate that the restrain effect of partial discharge spreading on the insulator surface by scratch or dielectric barriers. We prepared a few types of specimen for experiment to study the restrain effect of partial discharges on insulator. The 1 mm thick and 50 times 50 mm square plates made of polymethyl methacrylate (PMMA) were used for the experiments. One specimen had a scratch on the surface of PMMA. Another specimen had a couple of parallel polyimide tapes in the one side of the surface for the dielectric barriers. Each tape was pasted horizontally around center of the specimen and the interval of tapes was about 5 to 20 mm. From the experimental results, following conclusions were obtained. The dielectric barriers restrain the spreading of partial discharge on insulators surface. However, the restrain effects of barriers were weakened if the irradiating position of PD close to the dielectric barriers.