Surface flashover strength of different insulating materials in N/sub 2/-SF/sub 6/ gas mixtures under combined AC/DC voltages

Performance of insulating spacers in SF/sub 6/-N/sub 2/ gas mixture will be an important design factor in deciding the choice of spacer materials. In this study, 5 different polymers have been comparatively evaluated for surface flashover strengths in SF/sub 6/-N/sub 2/ gas mixtures of different proportions. The effect of AC, DC and combined AC/DC voltages on these spacer materials has been discussed. Compatibility of two different materials in terms of flashover behavior is also discussed. Though cycloaliphatic resin spacers show good performance, other spacer materials have distinct advantages in terms of surface tracking, bulk failure, and breakdown under combined and composite AC/DC voltages.