Optimum Analysis on Solid Dielectric Insulation Dimension in the Coaxial Electrodes Under Nanosecond Pulse Voltage

The majority of radial electric field declining in the very close vicinity of inner electrode results in very much non-uniform distribution of coaxial radial electric field in coaxial electrodes. Under the circumstance of invariable inner electrode diameter, increasing the diameter of outer electrode, the radial electric field decrease, following a stage of rapid decay, is markedly slowed down after the gap between the inner and outer electrodes is longer than a threshold; the same is only increasing the diameter of inner electrode as well as accordingly increasing the diameter of outer electrode, a given gap between inner and outer electrodes. After the inner electrode diameter passes a threshold because of the slight increment of diameter of inner electrode, the radial electric field also first decreases fast a very short stage, then evidently shows a flat process. The appearance of two thresholds about two parameters, the interval between inner and outer electrodes and the diameter of inner electrode, implies the optimum conception of the coaxial insulation structure of pulsed power equipments. This paper provides the empirical formula relevant to flashover length and the inner electrode diameter on the basis of the results of ANSYS software and experiments, the experimental results is of flashover data of polymethyl methacrylate(PMMA) and nylon 1010 in transformer oil under coaxial electric field under the applied pulsed voltage in the range of nanosecond.