SF6 Circuit Breaker

A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc.The pressure of gas is 5kg/cm2. It is odour-less, has high dielectric strength and high arc quenching force.It is a heavy gas. These are operated usually in the range of 3.3Kv-765Kv. And now mostly used at 765 Kv. The dielectric strength of SF6 is 2.5 times that of air.
This of 2 types.
1) Double pressure SF6 
2) Puffer type
It spoils the parts of C.B in moisture,to prevent this a mixture of (NaoH+Cao) is added in the chamber.
(this is a just a basic info about this circuit breaker,for further details search other blogs)