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A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. They are most often used for transmission-level voltages and may be incorporated into compact gas-insulated switchgear. In cold climates, supplemental heating or de-rating of the circuit breakers may be required due to liquefaction of the SF6 gas.

Advantages:

• Due to superior arc quenching property of sf6 , such breakers have very short arcing time
• Dielectric strength of sf6 gas is 2 to 3 times that of air, such breakers can interrupt much larger currents.
  
• Gives noiseless operation due to its closed gas circuit
  
• Closed gas enclosure keeps the interior dry so that there is no moisture problem
  
• There is no risk of fire as sf6 is non inflammable
  
• There are no carbon deposits
  
• Low maintenance cost, light foundation requirements and minimum auxiliary equipment
  
• sf6 breakers are totally enclosed and sealed from atmosphere, they are particularly suitable where explosion hazard exists
  

Disadvantages:

• sf6 breakers are costly due to high cost of sf6
• sf6 gas has to be reconditioned after every operation of the breaker, additional equipment is
  
• required for this purpose
  

See more:

• electricalandelectronics.org/2008/10/12/sulpher-hexa-flouride-sf6-circuit-breakers/