Comparison of PD phenomena in pure SF6 and N2-SF6 mixtures

Recently the research in breakdown and PD phenomena in pure SF₆ and gas mixtures is intensified due to a growing interest in the use of gas mixtures. In particular gas mixtures can be a very interesting substitute for pure SF₆ in large gas insulated systems, such as gas insulated lines. In this paper investigations on PD phenomena and breakdown voltages, performed in SF₆-N₂ mixtures containing 5% and 10% and pure SF₆, are presented. To make this comparison the influence of the test voltage and gas pressure was studied for different types of PD sources, such as protrusions and free moving particles. It is shown that differences can be observed in phase-resolved PD patterns, PD magnitude, UHF spectra and breakdown voltage