Static Field Breakdown of SF6-N2 Mixtures in Rod-Plane Gaps

The static field breakdown and corona characteristics of SF6-N2 mixtures in non-uniform field gaps for applied voltages of positive and negative polarities are discussed. Mixtures containing 0 to 100% SF6 are studied over a pressure range of 100 to 500 kPa. The results show that for such gaps, the dielectric behavior of SF6-N2 mixtures is very similar to that of pure SF6. A discontinuity is reported in the breakdown voltagepressure characteristics of SF6 and SF6-N2 mixtureswhen the rod electrode is positive. The pressure at which this discontinuity is observed is higher for the mixtures than for pure SF6 and is affected by the mixture ratio. The breakdown voltage for certain mixtures is up to 70% higher than that of pure SF6. When the rod electrode is negative, breakdown strength of N2 is very sensitive to the presence of small amounts of SF6 and is almost doubled if 0.2% of SF6 is added to N2. The breakdown and corona characteristics are discussed in detail.