SF6 Circuit Breaker



SF6 Circuit Breaker

  • SF6 is electro-nagative gas and its tendency very high and strong so that SF6 absorb free-electrones and SF6 Circuit Breaker full form is sulfur hexafluoride circuit breaker
  • When any fault occurs in the system that time contact will be open and arc produced between contact.
  • Then High pressure SF6 flow through the arc and last arc will be extinguished then the circuit breaker prevent from occurring any fault in the system. 

Is SF6 gas dangerous ? 

  • It is answer is No. because sf6 gas is non-flammable and non- toxic but sf6 high potent greenhouse gas.

SF6 circuit breaker construction

  • You can see below figure ,its diagram of circuit breaker.


  • In circuit breaker have two types of contact

Moving type contact

Fixed type contact  

  • To contact enclosed with the chamber it is also called as an interruption chamber and it is chamber containing a sf6 gas And this chamber Chamber is connected with sf6 gas reserver
  •  when contact will be arc open then Valve mechanism allowed to high pressure sf6 gas from reservoir  to flow by the arc interruption chamber
  • Fixed contact connected with the current carrying contact attach or fitted with the arc horn.
  • Moving contact is Hollow cylinder and it is connected with the rectangular holes in the sides allowed to sf6 gas
  • This unit consist of slide vents in moving contact which allow to very high pressure gas from the main tank.
  • Contact and arcing are coated with tungsten-copper Arc register material.
  • Hence this gas is costly so helping through suitable auxiliaries system sf6 is Re- conditional and reclaimed after each operation of breaker

SF6 Circuit Breaker Working 

  • When it will be displacement of the contact in condition of fault,that time very high pressure of sf6 at 14 kg/cm2 square flow from the reservoir to the arc interruption chamber.
  • SF6 is electro-nagative gas and its tendency very high and strong so that SF6 absorb free-electrones.
  • Then High pressure SF6 flow through the arc and last arc will be extinguished.
  • After this whole process reduced the high pressure of sf6 to low pressure And it will be stored in the low pressure reserver.
  • Then low pressure gas is pulled backed in high pressure reserver for reuse.

Advantages of SF6 Circuit Breaker

  • Sf6 gas is superior are quenching properties there for this circuit breaker have too many advantages compared to other circuit breaker like oil or Air circuit breaker some points of them are listed below..Such a circuit 
  1. Such circuit breakers have very short arcing time due to their properties of superior are quenching
  2. Sf6 gas has a good Die- electrical strength two to three times compared to air circuit breakers can interrupt much larger current
  3. The circuit breaker used noiseless operation due to its close gas and it is no over voltage problem because arc will be experience at the natural currents
  4. It is less maintenance required compared to an air system is a requirement.
  5. There are no carbon deposit so that insulation and tracking problem will be eliminated.
  6. Not any risks of the fire in this type of circuit breaker because property of Sf6 gas is non-inflammable.

Disadvantages of SF6 Circuit Breaker

  1. Such circuit breaker are costly compared to other circuit breaker due to the high cost of SF6 gas.
  2. Hence SF6 gas has to be reconditioned after each operation of the breaker, so that external equipment is required for this purpose.
  3. In the circuit breaker internal part needed cleaning between of fix under maintenance periods.

 Application of SF6 circuit breaker

  • This circuit breaker consist of interrupted unit and every unit capable of dealing with current upto 60 KVA and voltage will be in the range of 50-80 KVA.
  • Each unit connected with series in the system according to its the system voltage.
  • Nowadays SF6 circuit breakers have been developed for dealing for voltage 115 KV to 230 and power rating will be 10 MVA to 20 MVA and interrupting time less than 3 cycles.

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