Research Of Synergistic Effect Of C-C₄F₈ And Buffer Gas

SF₆ is a kind of perfect insulation gas,but it can cause worse greenhouse effect,so it’s necessary to find alternative gas for SF₆.Now the most possible alternative gas is electronegative gas.However,it must add buffer gas to lower liquefaction temperature of electronegative gas because of its high liquefaction temperature.What’s more,there may be synergistic effect between electronegative gas and buffer gas so that the gas mixtures can get better insulation characteristics.But the research about synergistic effect is not enough.c-C₄F₈ is a potential electronegative gas,but the realization of insulation characteristics and synergistic effect of c-C₄F₈ gas mixtures is not enough.This paper has researched the insulation characteristics and synergistic effect of gas mixtures composed of c-C₄F₈ and buffer gas N₂ and CO₂ respectively.This paper has introduced Boltzmann equation which is used in theoretical calculation and the experimental platform which is used in test.By calculating critical electric field and synergistic coefficient of c-C₄F₈/N₂ and c-C₄F₈/CO₂ gas mixtures,it shows that insulation characteristics of c-C₄F₈ gas mixtures are lower than SF6 when ratio of c-C₄F₈ is lower than 90%,and with the rise of c-C₄F₈,the insulation characteristics of c-C₄F₈ gas mixtures rise but the synergistic effect reduces.This paper limits the ratio of c-C₄F₈ lower than 35%by calculating the liquefaction temperature of c-C₄F₈ gas mixtures.This paper has measured power frequency breakdown voltage and lightning impulse breakdown voltage of c-C₄F₈、N₂、CO₂ and c-C₄F₈/N₂ and c-C₄F₈/CO₂ gas mixtures with10%and 30%c-C₄F₈ in slightly non-uniform electric field and extremely non-uniform electric field formed by sphere-plate electrode and needle-plate electrode respectively and calculated synergistic coefficient.It shows that30%c-C₄F₈/CO₂ gas mixtures are better to replace SF₆ in some conditions.As the rise of ratio of c-C₄F₈,synergistic effect of c-C₄F₈ gas mixtures will reduce,and synergistic effect of the same gas in extremely non-uniform electric field is higher than that in slightly non-uniform electric field,what’s more,synergistic effect of the same gas under power frequency voltage is higher than that under ligntning impulse voltage.The variation trend of synergistic effect of c-C₄F₈ gas mixtures is affected by gas pressure and gap distance,which generally increases as the gas pressure increases.Through the research on synergistic effect of c-C₄F₈ and buffer gas,this paper introduces synergistic effect of c-C₄F₈ mixture gas,providing certain reference for finding SF6 alternative gas and further studying synergistic effect of gas.