A comprehensive study of lightning impulse breakdown and cost/benefit analysis of ternary gas mixtures containing two electronegative gases

The ever increasing voltage levels in modern power transmission systems have stimulated considerable interest in the use of strongly attaching gases of high dielectric strength such as SF/sub 6/ and CCl/sub 2/F/sub 2/ as insulants. Because of the high cost of such gases, the economic considerations have necessitated research towards obtaining binary and ternary mixtures of these gases (SF/sub 6/ and CCl/sub 2/F/sub 2/) with unitary gases like N/sub 2/, CO/sub 2/ and air, for practical applications. If a small quantity of SF/sub 6/ is added to N/sub 2/ or CO/sub 2/ in combination with a fluorocarbon gas such as CCl/sub 2/F/sub 2/, this results in a considerable increase in the dielectric strength of the mixture at reduced cost. This paper discusses the lightning impulse (1.2/50 /spl mu/s) breakdown characteristics obtained with different SF/sub 6//CCl/sub 2/F/sub 2//N/sub 2/ and SF/sub 6//CCl/sub 2/F/sub 2//CO/sub 2/ mixtures using 5 mm diameter rod-230 mm diameter plane electrode geometry over the pressure range of 0.1 to 0.5 MPa (1 to 5 bar) at a constant gap of 20 mm.