The influence of the dielectric strength of the N/sub 2//SF/sub 6/-insulation by conducting particle on the spacer surface

This paper investigates the dielectric properties of various N/sub 2//SF/sub 6/ gas mixtures based upon a cylindrical spacer model with adhering particle on the surface tinder homogeneous field conditions. The investigation involves a comparison with pure SF/sub 6/. The flashover field strength for clean and particle contaminated spacer surface under AC and LI stress is determined. The results of the investigations show the sensitivity of N/sub 2//SF/sub 6/ gas mixtures to conducting particles on spacer surfaces for gas pressures up to 800 kPa. Moreover, the correspondence between pure SF/sub 6/ at pressure range from 100 to 400 kPa and N/sub 2//SF/sub 6/ gas mixtures for AC and lightning impulse (LI) flashover field strength range from 50 to 178 kV/cm is determined. Conclusions are drawn about the ability of SF/sub 6/ gas mixtures to serve as technically efficient media for GIS/GITL. The results shed light on the issue of the SF/sub 6/ reduction and particle detectability in GIS/GITL.