Effect of Oxygen on Power Frequency Breakdown Characteristics and Decomposition Properties of C5-PFK/CO2 Gas Mixture

Abstract

This study explores the effect of O<inf>2</inf> as the second-component buffer gas on the power frequency breakdown characteristics and decomposition products of C5-PFK/CO<inf>2</inf> gas mixture. It is found that the breakdown voltage of C5-PFK/CO<inf>2</inf> gas mixture containing 7.5% C5-PFK is about 1.4 times that of CO<inf>2</inf> gas and about 2/3 of SF<inf>6</inf> gas at the same pressure. Although the average breakdown voltage of C5-PFK/CO<inf>2</inf>/O<inf>2</inf> gas mixture is slightly lowered, the addition of O<inf>2</inf> reduces the standard deviation of the breakdown voltage, improving the insulation stability of the C5-PFK/CO<inf>2</inf> gas mixture. The decomposition by products of C5-PFK/CO<inf>2</inf> gas mixture include CO, CO<inf>2</inf>, CF<inf>4</inf>, COF<inf>2</inf>, C<inf>2</inf>F<inf>4</inf>, C<inf>2</inf>F<inf>6</inf>, C<inf>3</inf>F<inf>6</inf>, C<inf>3</inf>F<inf>6</inf>0, C<inf>3</inf>F<inf>8/</inf>, C<inf>4</inf>F<inf>10</inf>, CHF<inf>3</inf>, C3HF7 and other fluorocarbon compounds. C5-PFK/CO<inf>2</inf>/O<inf>2</inf> gas mixture with 4% O<inf>2</inf> produces much CF<inf>4</inf>, C<inf>2</inf>F<inf>6</inf> and less CO after breakdown. It is recommended to add 4 to 6% O<inf>2</inf> in C5-PFK/CO<inf>2</inf> gas mixture to improve the power frequency breakdown characteristics for engineering application.