Sulfur hexafluoride gas is known to have two properties.One is physical properties.Pure SF6 gas colorless,tasteless,non-toxic,non-combustion,is an inert gas.Under the pressure of 0.098MPa,the specific gravity relative to air is 5.19(6.9/1.29),and the liquefaction temperature is-62℃.And the other one is chemical.SF6 gas is insoluble in water and transformer oil,at the temperature below 800℃is still an inert gas,not burning,at the hot temperature is not with hydrogen,oxygen,aluminum,copper and many other substances,water,acid,alkali will not make it decompose.

　　Under normal conditions,sulfur hexafluoride gas is colorless and tasteless,and has good insulation and arc extinguishing properties.Once the moisture in the atmosphere is immersed or the surface of the solid medium is damp,the electrical strength will decrease significantly.Circuit breaker is outdoor equipment,when the temperature plummets,SF6 gas excess water may condense on the surface of the solid medium and flashover occurs,causing a serious breaker explosion accident.Pure SF6 gas,in operation,by the arc discharge or high temperature,will be decomposed into monomer fluorine,sulfur and sulfur compounds,the arc will disappear and combined into stable SF6 gas.

　　When the sulfur hexafluoride gas containing moisture,the emergence of fluoride sulfur compounds can react with water to generate strong corrosive of hydrofluoric acid,sulfuric acid and other highly toxic chemicals,etc.,endanger the life safety of the maintenance staff,insulating material of circuit breaker or cause corrosion of metal material,make the insulation deterioration,even equipment explosion.

　　Therefore,it is impossible to completely remove the moisture of SF6 gas in the high-purity sulfur hexafluoride circuit breaker,but to master the causes of SF6 gas moisture exceeding the standard,take corresponding prevention and control measures,reduce the moisture in SF6 gas,can ensure and improve the safe operation reliability of the circuit breaker.