Monitoring of the dielectric strength of the air/SF6-mixtures for application in gas insulated transmission lines

Abstract

This paper investigates the dielectric properties of various air/SF 6 gas mixtures based upon a cylindrical spacer model with adhering particle on the surface under homogeneous field conditions. The investigation involves a comparison with pure SF 6 . The flashover field strength for clean and particle contaminated spacer surface under lightning impulse (LI) and alternating voltage (AC) stress is determined. The results of the investigations show the sensitivity of air/SF 6 gas mixtures to conducting particles on spacer surfaces for gas pressure up to 1000 kPa. Moreover, the correspondence between pure SF 6 and air/SF 6 gas mixtures for AC and LI flashover field strength range from 50 to 178 kV/cm is determined. Conclusions are drawn about the ability of air/SF 6 gas mixtures to serve as technically efficient media for long Gas Insulated Transmission Lines (CIITL). The results shed light on the issue of the SF 6 reduction and the particle detectability in GITL.