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

This paper studied the insulation characteristics of C
₃
F
₈
gas mixtures with N
₂
and CO
₂
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 C
₃
F
₈
-N
₂
and C
₃
F
₈
- CO
₂
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 C
₃
F
₈
-N
₂
gas mixture is greater than that of C
₃
F
₈
-CO
₂
for C
₃
F
₈
gas content k varied from 0% to 100%, and the C
₃
F
₈
-N
₂
gas mixture containing 20% proportion C
₃
F
₈
can achieve 60% dielectric strength of pure C
₃
F
₈
. Additionally, the synergistic effects of the insulation strength for C
₃
F
₈
gas mixtures are also evaluated and compared with that of SF
₆
-N
₂
mixture. The calculation results, together with the discussions on liquefaction temperature and global warming potential indicate that gas mixtures containing C
₃
F
₈
are feasible for applying in electric power apparatus as insulation medium.