Comparison of SF/sub 6//N/sub 2/ and SF/sub 6//CO/sub 2/ gas mixtures as alternatives to SF/sub 6/ gas

The interest in SF/sub 6/ gas mixtures has been re-ignited in recent years by the issue of the greenhouse effect of the SF/sub 6/ gas, and most research work is now focused on a SF/sub 6//N/sub 2/ gas mixture, which is suitable for application in electrical apparatus with slightly non-uniform fields. This paper presents a comparison of SF/sub 6//N/sub 2/ and SF/sub 6//CO/sub 2/ gas mixtures with a viewpoint of their possible applications to gas-insulated transformers, where both highly non-uniform field problems and partial discharges in gas/film insulation are inevitable. It is shown that in this case the dielectric strength of SF/sub 6//CO/sub 2/ is superior to that of SF/sub 6//N/sub 2/ with a minor disadvantage related to the gas decomposition in SF/sub 6//CO/sub 2/. However, this may not be a problem for the SF/sub 6//CO/sub 2/ gas mixture to be used in gas-insulated transformers, where internal breakdown is not allowed.

[1]  Y. Qiu,et al.  Effect of electrode surface roughness on breakdown in SF6-N2 and SF6-CO2 gas mixtures , 1993 .

[2]  R. J. Van Brunt,et al.  SF/sub 6//N/sub 2/ mixtures: basic and HV insulation properties , 1995 .

[3]  Y. Qiu,et al.  LETTER TO THE EDITOR: Measurement of ionisation and attachment coefficients in difluorodichloromethane and SF6 gas mixtures , 1987 .

[4]  A. Pedersen,et al.  On the Assessment of New Gaseous Dielectrics for GIS , 1985, IEEE Transactions on Power Apparatus and Systems.

[5]  N. Malik,et al.  Breakdown Gradients in SF6-N2, SF6-Air and SF6-CO2 Mixtures , 1980, IEEE Transactions on Electrical Insulation.

[6]  E. Kuffel,et al.  Dielectric strengths of SF6/N2 and SF6/CO2 gas mixtures at low pressure-gap separation values , 1988 .

[7]  N. Malik,et al.  A Review of Electrical Breakdown in Mixtures of SF6 and Other Gases , 1979, IEEE Transactions on Electrical Insulation.

[8]  Y. Qiu,et al.  A New Approach to Measurement of the Figure-of-Merit for Strongly Electronegative Gases and Gas Mixtures , 1987, IEEE Transactions on Electrical Insulation.

[9]  Y.P. Feng,et al.  Investigation of SF/sub 6/-N/sub 2/, SF/sub 6/-CO/sub 2/ and SF/sub 6/-air as substitutes for SF/sub 6/ insulation , 1996, Conference record of IEEE International Symposium on Electrical Insulation.

[10]  Y. Qiu,et al.  Factors affecting partial discharges in SF/sub 6/ gas impregnated polymer film insulation , 1988, Proceedings., Second International Conference on Properties and Applications of Dielectric Materials.