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Sunday, 5 April 2020

What is SF6 Circuit Breaker? Working, Construction, Advantages, Applications

Circuit Breaker in which SF6 gas under pressure is used to extinguish the arc is so it is called SF6 circuit breaker.

SF6 means Sulphur Hexafluoride gas. It has excellent dielectric, arc quenching, and other physical properties. So this is used in circuit breaker.

SF6 circuit breaker are used in high voltage transmission and distribution systems. Because it has excellent arc breaking capacity.  In this there is no risk of fire or explosion. 

SF6 Circuit Breaker
SF6 Circuit Breaker


Construction of SF6 Circuit Breaker


Construction of SF6 circuit Breaker
      Construction of SF6 circuit Breaker

The construction of SF6 circuit breaker is simple in kind of other 
Circuit breakers. There are main two contact and fixed contact. 

This two contacts are placed in the interruption chamber. Then the SF6 gas is reservoir is connected to that interruption chamber. 

When the contacts of CB opens then it allows to high pressure SF6 gas from reservoir to flow towards the interruption chamber. 

Both the contacts and arcing horn are coated with the copper tungsten material which is arc resistant material. 

This contacts are fixed like hollow cylindrical shape. Moving contacts contains rectangular which has holes in sides to allow the SF6 gas go through these holes flowing and across the arc.

This gas is recycled and reused by the suitable auxiliary system after every operation or use of breaker. This is because of the SF6 gas is costly.

Working Of SF6 Circuit Breaker

  The contacts of circuit breaker are closed at the normal operating condition of working.

When some fault occurs in the system contacts are open and arc is struck between them.

The movement of moving contacts cause to occur operate valves at the same time which enters the high pressure SF6 gas in the arc interruption chamber at some pressure.

This SF6 gas absorbs free electrons in the arc path and forms ions that ions does not carries the charge. This ions increases the dielectric strength of the gas and hence the arc get extinguished. 

This gas is stored in low pressure reservoir and this is pulled back to high pressure reservoir for reuse it.

Advantages of SF6 Circuit Breaker

 The atmospheric conditions does not affects on the performance of the SF6 circuit breaker.

The cost of it is less due to compressed air system is required.

Maintanence of this circuit breaker is less.

  It has high dielectric strength so the electric clearance gets reduced.

Arc gets extinguished at natural current zero so there is no voltage problem. There is no risk of fire.

The gas used is non-inflammable and it has chemically stable.

  Same gas is re- circulated into the circuit there by reducing the requirement of SF6 gas.

The SF6 CB can  perform various duties like clearing short line faults, opening unloaded transmission line, capacitor switching transformer reactor switching etc. Without any problem.


Disadvantages of SF6 Circuit Breaker

The parts in CB needs more cleaning during periodic maintenance under clean and dry environment.

It causes failure when the moisture enters in CB.

The SF6 gas is too costly and it needs more facility for transformation and maintanence of quality of gas.

 Arced SF6 gas is poisonous and should not be inhaled.

Applications of SF6 Circuit Breaker

  Used for high voltage Applications

For switching related to high voltage and extra high voltage applications.


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