Analysis of the insulation characteristics of c-C₄F₈/CO₂gas mixtures by the Monte Carlo method

This paper analyses the insulation characteristics of c-C 4 F 8 /CO 2 gas mixtures using the Monte Carlo method with the null-collision technique and studies the possibility of applying that in the gas insulation of power equipment. The density-normalized effective ionization coefficient (α − η)/ N for c-C 4 F 8 /CO 2 gas mixtures has been calculated using a sample of a pulsed Townsend discharge. The overall density-reduced electric field strength ( E / N ) could be varied between 150 and 450 Td (1 Td = 10 −17 V cm 2 ), while the c-C 4 F 8 content in the gas mixtures is varied over the range 0–100%. From the variation curve of (α − η)/ N with the c-C 4 F 8 mixture ratio k , the limiting field ( E / N ) lim of the gas mixture at different gas contents is determined. The required gas pressure ratios comparable to the insulation property of SF 6 and the global warming potential (GWP) at this gas pressure were also investigated. It is found that the limiting field ( E / N ) lim of the c-C 4 F 8 /CO 2 gas mixtures is higher than that of SF 6 /CO 2 gas mixtures, and the GWP of the former is significantly lower than that of the latter.