In this paper

the power frequency breakdown test of SF

6

gas at hemispherical rod plate electrode at the temperature ranged from-50 ℃ to 20 ℃ is performed for the purpose of mastering the low temperature discharge characteristics of SF

6

gas and assuring the operation reliability of SF

6

gas equipment in low temperature environment. At the same time

the variation of SF

6

gas pressure with temperature is measured. The variation law of discharge voltage of SF

6

gas

at absolute pressure at 0.7 MPa and 0.5 MPa in the slightly inhomogeneous electric field with temperature is obtained. It is found that when the temperature decreases from 20 ℃ to-50 ℃

the discharge voltage and pressure of SF

6

gas show the tendency of initially slow decrease and then fast decrease. The inflection of discharge voltage decrease tendency is basically identical to that of gas pressure decrease tendency. It is found by calculation that the temperature of the inflection point is equal to the liquefaction temperature of SF

6

gas. The test phenomena are explained by gas discharge theory. It is pointed out that the density of SF

6

gas is reduced by its liquefaction

thus causing the reduction of its discharge voltage. Furthermore

the relationship between the liquefying temperature and the pressure of SF

6

gas is calculated

which provides a reference for the safe operation of SF

6

gas equipment at low temperature.