Study of the dielectric breakdown strength of CO2-O2 mixtures by considering ion kinetics in a spatial-temporal growth avalanche model

The gas mixture CO2-O-2 has been considered as an insulation and arc-quenching medium in gas-insulated switchgears. In this paper, the dielectric breakdown properties of CO2-O-2 mixtures at different O-2 concentrations and gas pressures were studied theoretically by considering ion kinetics in a spatial-temporal growth avalanche model. A kinetic scheme that includes all the main reactions likely to occur in CO2-O-2 mixtures is presented. An improved method to calculate the dielectric strength of the gas mixture is developed, based on an avalanche model that considers both spatial growth and temporal processes. Next, the reaction rates of ionization, attachment, detachment and ion conversion, the effective ionization Townsend coefficient aeff/N, and reduced critical electric field strength (E/N) cr in CO2-O-2 mixtures at different mixing ratios and gas pressures are analyzed in detail. Finally, a pulsed Townsend experiment is performed to verify the validity and accuracy of the calculation method. Based on this, one detachment reaction rate is modified to yield more accurate results. Better consistency between the results and the experimental values supports the validity of the kinetic system, reaction rates, and the improved calculation method.

Automated summary

In this paper, the dielectric breakdown properties of CO2-O-2 mixtures at different concentrations and pressures were studied. A kinetic scheme that includes the main reactions in the mixtures was presented, and an improved calculation method for dielectric strength was developed. The reaction rates and electric field strength in the mixtures were analyzed, and the validity of the calculation method was verified through experiments.