Electrode Surface Roughness Effect on the Breakdown Characteristics of Compressed Gas Cable

Abstract

The influence of electrode surface roughness on the breakdown field strength in SFu gas and mixtures is investigated. A coaxial electrode configuration is used to represent a practical gas insulated cable. With the use of an approximate formula for the effective ionization coefficient and the streamer discharge criterion, it is possible to calculate the breakdown field strength both in SFs and in mixtures. The factors influencing the deterioration of the dielectric strength of SF6 gas and mixtures with air, CO; and N2 are discussed. A comparison between results obtained for SF^ gas is presented. The results confirm that increased electrode surface roughness leads to reduced breakdown voltages of compressed gas insulated systems.