Lightning impulse withstand performance of a practical GIC with 5 and 10 percent SF/sub 6//N/sub 2/ mixtures

This publication presents the results of dielectric tests performed on a scale model GIC with mixtures of N/sub 2/ and SF/sub 6/. The purpose of these tests were to establish the allowable design stress levels for the power frequency, BIL and SIL ratings of the 420 GIC system with mixtures of N/sub 2/ and SF/sub 6/ where SF/sub 6/ is the minority constituent. The goal was to optimize a system that would utilize less than 30% SF/sub 6/. The test model had the same geometry, conductor surface finish and insulators as the 242 kV commercial system currently offered by ABB. The results from the tests were used to establish the dielectric design parameters for the 420 kV GIC system as well as the satisfactory ratios of SF/sub 6/ in N/sub 2/, (SF/sub 6//N/sub 2/).