Charging mechanisms of polymer spacers electrically stressed in SF₆ environment

摘要

An attempt is made to elucidate the mechanisms causing chargeaccumulation on and inside insulating spacers. The experiments wereconducted inside a glass cruciform vessel which could be evacuated to 10-2 torr and had a maximum SF₆ working pressure of2 bar. Cylindrical spacers of polytetrafluorethylene and polyethylene(diameter 20 mm, height 10 mm) were investigated. The chargeaccumulation on smooth-surfaced insulators was controlled by threemechanisms: dielectric polarization producing heterocharge, surfacecharge injection from the electrode, and bulk injection from theelectrode. The charge accumulated was of the same polarity as theapplied voltage. The rough-surfaced insulator produced chargedistributions which had charge densities higher than those of thecomparable smooth-surfaced insulator