Optimal profiles of disc-type spacers for gas insulation

By adopting the suitable contact angle of a disc-type spacer, the surface flashover may be effectively suppressed on account of the decrease of the maximum field strength at the spacer surface. The calculation has clarified that the optimal contact angle of the spacer is 60¿70° according to the relative permittivity of the spacer for R2/R1 (ratio of inner and outer electrode radii) = 1/3, and that 20¿30% decrease in the maximum strength can be brought about in various spacer-electrode arrangements. The effect on the field-relaxation of R2R1, the relative permittivity of the spacer, and the spacer shape have been studied. Experiments in air at atmospheric pressure and in compressed SF6 have verified that very few flashovers take place at the surface of the field-relaxing spacers.