Dielectric Strength of 9%C4F7N/91%CO2 Gas Mixture Under Three Typical Voltage Waveforms

In order to master the dielectric strength of the environment friendly insulating gas C 4 F 7 N/CO 2 mixture under different voltage waveforms, so as to provide the basis for its replacement of SF 6 ,. The breakdown tests of 9%C 4 F 7 N/91%CO 2 gas mixture under power frequency, lightning impulse and switching impulse voltages are carried out with plate-plate electrode, and the test results are compared with SF 6 , under the same pressure. The results show that the breakdown voltage of 9% C 4 F 7 N/91%CO 2 gas mixture is higher than 80% of SF 6 , at the same pressure under three kinds of voltage, which indicates that the optimized ratio has a certain application prospect. The breakdown voltage under switching impulse voltage waveform is lower than the power frequency breakdown voltage and lightning impulse breakdown voltage under the same conditions, which indicates that the rise steepness of voltage waveform has a certain influence on the breakdown voltage even in a nearly uniform electric field. In addition, it is also found that whether the electrode is polished or not will also have a significant impact on the breakdown voltage, which should be paid special attention to in gas breakdown test.