A study on the breakdown characteristics of the fluorocarbon

In this paper, we investigated physical properties and electrical characteristics of the fluorocarbon used as coolants for large power gas-insulated transformers. Volume resistivity of the fluorocarbon is /spl rho/=1.87/spl times/10/sup 15/ [/spl Omega//spl middot/cm] at 1 atm, 27/spl deg/C. Dielectric constant is 1.86 and decreases as temperature increases. The breakdown voltage at 1 atm is higher than that of transformer oil. The breakdown voltage of fluorocarbon vapor is about 18 kV when pressure in a test chamber increases over 1 kg/cm/sup 2/. When fluorocarbon is mixed with SF/sub 6/ gas, breakdown voltage of the mixture is higher than that of fluorocarbon. Then fluorocarbon leads to an increase over 4 kg/cm/sup 2/ in pressure as the temperature increases. Therefore, when a gas-insulated transformer is manufactured, the design must be taken into consideration at high-pressure.