Comparison of the first negative corona current pulses in N2 + SF6 and CO2 + SF6 mixtures

Abstract

The current waveforms of the first negative corona pulses in a small point-to-plane gap have been measured with a nanosecond time resolution in N2 + SF6 and CO2 + SF6 mixtures at a pressure 50 kPa for various contents of SF6 as a function of applied gap voltages. The physical mechanism for the pulses in these mixtures with low concentration of SF0 has been described using the streamer-based theory. The influence of changing admixtures of SF6 in N2 and CO2 has been compared. Differences in the pulse waveforms observed in N2-and CO2-based gas mixtures are explained by differences in the first and second Townsend ionization coefficients. : 52.80.-s, 51.50.+v PACS