The influence of the dielectric strength of the N2/SF6-insulation by conducting particle on the spacer surface

This paper investigates the dielectric properties of various N₂/SF₆ 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 SF₆. 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 N₂/SF₆ gas mixtures to conducting particles on spacer surfaces for gas pressures up to 800 kPa. Moreover, the correspondence between pure SF₆ at pressure range from 100 to 400 kPa and N₂/SF₆ 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 SF₆ gas mixtures to serve as technically efficient media for GIS/GITL. The results shed light on the issue of the SF₆ reduction and particle detectability in GIS/GITL.