Dielectricc Strength of Gas Mixtures Comprising SF6, CO, c-C4-F8 and SF6, N2, c-C4F8

In a previous paper[8] breakdown strengths of c-C4F8/SF6/CO gas mixtures in various proportions were reported for a 30mm rod-sphere gap under ac and impulse voltages. A mixture of 1% c-C4F8 + 59% SF6 + 40% CO exhibited higher dielectric strength than pure SF6 in the pressure range between 350 and 400 kPa. The present paper compares CO and N2 as a buffer in gas mixtures and extends the studies to a nearly uniform field gap and a highly non-uniform field gap. Additional experiments comfirmed that the use of CO as a buffer in gas mixtures is superior to N2 and that some c-CZF8/SF6/CO gas mixtures have higher dielectric strength and are cheaper than pure SF6.