Analysis of the insulation characteristics of C3F8 gas mixtures with N2 and CO2 using boltzmann equation method

This paper studied the insulation characteristics of C₃F₈ gas mixtures with N₂ and CO₂ from the point view of electron swarm parameters. The density-normalized effective ionization coefficient (α-η)/N and electron drift velocity V_e in binary C₃F₈-N₂ and C₃F₈- CO₂ gas mixtures are calculated by solving the Boltzmann equation in the condition of steady-state Townsend discharge experiment. Values of the limiting electric field strength for which the electron ionization exactly balances the attachment are derived from the effective ionization coefficient data. It is found that the limiting field strength of C₃F₈-N₂ gas mixture is greater than that of C₃F₈-CO₂ for C₃F₈ gas content k varied from 0% to 100%, and the C₃F₈-N₂ gas mixture containing 20% proportion C₃F₈ can achieve 60% dielectric strength of pure C₃F₈. Additionally, the synergistic effects of the insulation strength for C₃F₈ gas mixtures are also evaluated and compared with that of SF₆-N₂ mixture. The calculation results, together with the discussions on liquefaction temperature and global warming potential indicate that gas mixtures containing C₃F₈ are feasible for applying in electric power apparatus as insulation medium.