Solid insulated switchgear (SIS) has been developed as a substitution for medium voltage SF6 gas insulated switchgear. Its main circuits including a vacuum interrupter are coated with epoxy resin and a solid/gas insulation system is formed. For further miniaturization and higher stress design, the authors investigated the surface insulation performance of the solid/gas insulation system containing an embedded electrode. In the previous study, the authors investigated the surface breakdown characteristics. The authors also investigated the surface discharge propagation characteristics and proposed an estimation method of the surface breakdown voltage. In the present study, the authors investigated the surface breakdown characteristics numerically. The calculation was done based on the estimation method proposed previously. The divided voltage ratio, the radius of the embedded electrode, the enhancement factor of the surface insulation strength and the peak value of the surface breakdown voltage are examined. As a result, the characteristics of the parameters and the criteria for the optimum insulation design were clarified.

Solid insulated switchgear (SIS) has been developed as a substitution for medium voltage SF6 gas insulated switchgear. Its main circuits including a vacuum interrupter are coated with epoxy resin, therefore, a solid/gas insulation system is formed. For further miniaturization and higher stress design of SIS, the authors investigated on the surface insulation of the solid/gas insulation system containing an embedded electrode. In the present study, the surface breakdown voltage was estimated based on the surface discharge propagation characteristics. From the measurement of the surface flashover voltage on a dielectric against the surface distance, the relation between the surface flashover voltage and the surface distance was found to be expressed with an equation derived from the empirical equation presented by Toepler. Then, the surface breakdown voltage was estimated based on the obtained equation. The estimated values were compared with the experimental data obtained varying a parameter of the radius of the embedded electrode, thickness of the epoxy resin plate or the radius of the plate. As a result, a good correlation was obtained. Therefore, the estimation method of the surface breakdown voltage on the solid/gas insulation with embedded electrode was established.

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