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, Vs, with small percentages of electron-attaching additives. The effect of electron-dipole scattering on Vs 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 Vs and suggest that a careful combination of gases slowing down electrons via dipole scattering and via negative ion states can effect large Vs 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.

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