Dielectric gas mixtures with polar components

Dielectric gas mixtures comprising mainly one electron-attaching component and one dipolar component have been investigated. It has been found that polar electron-slowing-down components effect a sharp increase in the breakdown voltage, V s , with small percentages of electron-attaching additives. The effect of electron-dipole scattering on V s for multicomponent gas dielectrics is assessed, especially in combination with indirect electron scattering via negative ion states. The results demonstrate further the beneficial effect of large electron scattering cross-sections at subexcitation energies on V s and suggest that a careful combination of gases slowing down electrons via dipole scattering and via negative ion states can effect large V s values. This and earlier studies suggest that a number of dielectric gas mixtures containing one or two electron-attaching components from c-C 4 F 8 , 2-C 4 F 8 , SF 6 and a dipolar component from CHF 3 , CH 2 F 2 or 1,1,1-CH 3 CF 3 with or without N 2 are excellent candidates for large-scale testing for possible eventual industrial adoption.