Experimental Investigation of the Breakdown Voltage of CO2, N2, and SF6 Gases, and CO2-SF6 and N2-SF6 Mixtures under Different Voltage Waveforms

This paper is devoted to a comparison study of the breakdown voltage of CO2, N-2, and SF6 gases, and CO2-SF6 and N-2-SF6 mixtures under different voltage waveforms, namely AC, DC, and lightning impulse voltages, in point-plane and sphere-sphere electrode arrangements. The influence of pressure, voltage polarity, and percentage of SF6 in CO2 and N-2 were studied, and equivalencies between the breakdown voltage of SF6 and those of the considered mixtures were analyzed. It is shown that the breakdown voltage of SF6 is the highest, whatever the applied voltage waveforms. Similarly, for a given voltage waveform, the breakdown voltage of SF6 is the highest. The AC breakdown voltage is the lowest for all gases. The addition of small amounts of SF6 to CO2 and N-2 significantly improved the breakdown voltages of both natural gases. For a given breakdown voltage, the ratio between the pressure of CO2 to that of SF6 was generally lower than the pressure of N-2 to SF6, whatever the voltage waveforms.