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-C₄F₈, 2-C₄F₈, SF₆ and a dipolar component from CHF₃, CH₂F₂ or 1,1,1-CH₃CF₃ with or without N₂ are excellent candidates for large-scale testing for possible eventual industrial adoption.