Properties and application of the SF6/CF2CL 2 gas mixtures

The Townsend first ionization and electron attachment coefficients were measured in SF₆/CF₂/Cl₂ gas mixtures using the steady-state Townsend method, and the optimal mixing ratio was found to be around 50/50. The breakdown strength of the 50/50 gas mixture in a uniform field gap or a slightly nonuniform field gap was higher than that of SF₆ gas by 5%. Carbon deposition phenomena were studied in the sparked gas mixture both by visual observation and by mass spectrometry and Auger electron spectroscopy. Experiments showed that the SF₆ concentration in the 50/50 gas mixture was sufficient for carbon inhibition upon sparking. Finally, a 100 kV prototype standard capacitor filled with the 50/50 gas mixture is described. The total gas pressure is 0.4 MPa, which allows the capacitor to be used in laboratories where the lowest temperature is above -12°C