Research on the synergy of SF6/N2 mixture gas in low temperature environment

Abstract

For high latitudes, due to the deficiencies of liquefaction of SF6 and extreme greenhouse effect, gas-insulated metal-enclosed switchgear (GIS), gas-insulated metal-enclosed transmission lines (GIL) and other electrical equipment have begun to use mixed gas of SF6 and N2 as the insulation medium. For this purpose, slightly non-uniform electric field distribution is generated using hemisphere-plane electrodes. Under the excitation of a negative DC high voltage, the breakdown voltage of the SF6/N2 mixture gas is measured at a temperature of 0 to -15°C and a gas pressure of 15 to 60 kPa. The voltage is used to calculate the synergistic coefficient of the mixed gas, and the effect of the temperature and pressure on the synergy of the mixed gas is analyzed. The results show that under slightly non-uniform electric field conditions, the synergy of the mixed gas decreases with decreasing temperature, and increases with increasing gas pressure. It follows that good insulating property of SF6/N2 gas mixture used in a low temperature environment can be achieved by selecting a reasonable temperature and gas pressure.