Analysis of the insulation characteristics of c-C4F8and N2gas mixtures by Boltzmann equation method

Abstract

The present paper concerns itself with the insulation characteristics of c-C 4 F 8 /N 2 gas mixtures and studies the possibility of applying in the gas insulation of power equipments. We aim to use the theoretical framework of the Boltzmann equation to calculate the density-normalized effective ionization coefficients ( α – ƞ )/ N and transport parameters of c-C 4 F 8 /N 2 gas mixtures for E / N values from 180 to 550 Td (1 Td = 10 −17 V cm 2 ) in the condition of steady-state Townsend (SST) experiment. From the variation curve of ( α – ƞ )/ N with the c-C 4 F 8 mixture ratio k , the limiting field strength ( E / N ) lim of the gas mixtures at different gas content is determined. In order to confirm the validity of the results obtained, comparisons with Monte Carlo simulation and experimental data have been performed. It is found that the insulation properties of c-C 4 F 8 and N 2 gas mixtures are much better than those of SF 6 and N 2 mixtures for applying in the high voltage apparatus as an insulation medium, especially if we take the global warming potential into account.