Dielectric Properties of HFC-134a mixtures with CO2 as a possible SF6-substitute gas

Environmental friendly fluorinated compounds and their mixtures with CO2 are considered as a typical category of SF6-substitute gases, due to their low global warming potentials and good dielectric strength. This paper investigates the breakdown characteristics and physical and chemical properties of HFC-134a (1,1,1,2,3,3,3-Heptafluor-opropane) and its mixtures theoretically and experimentally, which are compared with those of SF6. The results show that the HFC-134a mixtures with CO2 are suitable for the power application with pressure 0.1 MPa, such as medium voltage power equipment. Espeically for the power application with 0.3MPa, the HFC-134a/CO2 mixtures with the same pressure or a higher pressure could have equivalent insulation as SF6, whose GWPs are almost one twenty-third that of SF6. For the power application with 0.5 MPa, the HFC-134a/CO2 mixtures with the liquefaction temperature -15°C and pressure 0.6 MPa could have equivalent insulation as SF6.