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The electron swarm parameters in c-C4F8/CO2 gas mixtures, including the density-normalized effective ionization coefficient (α-η)/N and the drift velocity Ve, are calculated for the overall density-reduced electric-field strength E/N values from 150 to 600 Td (1 Td = 10-17 V · cm2). These calculations have been performed through solving the Boltzmann equation under the two-term approximation in the condition of steady-state Townsend experiment. The c-C4F8 content k in the gas mixtures can be varied over the range of 0%-100 %. From the variation curve of (α-η)/N with the c-C4F8 mixture ratio k, the limiting field strength (E/N)lim for each c-C4F8 concentration is determined for the analysis of the insulation characteristics of the c-C4F8/CO2 mixture. Additionally, the global-warming potential and the liquefaction temperature of c-C4 F8/CO2 gas mixtures are also taken into account to evaluate the possibility of applying in gas insulation of power equipment.
Date of Publication: Oct. 2012