Why use SF6 gas in a circuit breaker?
Sulfur hexafluoride (SF6) gas is used in circuit breakers because it has superior insulating and arc quenching properties far better than air or oil.
It has high dielectric strength and high cooling effects, and quickly recombines after arc breaking. SF6 is a highly stable, non-toxic, and non-flammable gas that is used as an insulating and arc-quenching medium in high-voltage circuit breakers.
It also has a unique property of quick recombination after arc breaking and is usually a good transfer of heat energy.
SF6 circuit breakers protect electrical power stations and distribution systems by interrupting electric currents when tripped by a protective relay.
Instead of oil, air, or a vacuum, an SF6 circuit breaker uses SF6 gas to cool and quench the arc on opening a circuit.
Advantages over other media include lower operating noise and no emission of hot gases, and relatively low maintenance.