Oil Circuit Breaker (ocb) – Types, Construction, Working and Applications ocb – Oil Circuit Breaker – Construction and Working Principle

Arc Control Oil Circuit Breaker
Such BOCB includes a special system designed to control the arc to efficiently quench it. These designs enable the CB to extinguish the arc even if the contact gap is small. Unlike plain-break OCB, these CBs can be used in high voltage circuits.
The arc control Oil circuit breaker can be classified into the following two types.

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  Self-Blast Oil Circuit Breaker
  
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  Forced Blast Oil Circuit Breaker
  

Self-Blast Oil Circuit Breaker- In such OCB, the arc is controlled by internal means such as the energy of the arc is used for its own extinction.
Forced Blast Oil Circuit Breaker- In such OCB, the arc control is provided by external means.
Self-Blast Oil Circuit Breaker
In self-blast OCB, the contacts are surrounded by a chamber called pressure chamber or explosion pot. It is made from insulating material. The gas produced by the arc is accumulated inside the pressure chamber. It has a small volume thus having high pressure. The amount of pressure exerted is directly proportional to the arc current. It reduces the contact gap required for successful arc extinction, as well as reduces the arcing time.
Self-blast oil circuit breaker’s explosion pot can be designed in the following designs each providing its own benefits.

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  Plain Explosion Pot
  
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  Cross Jet Explosion Pot
  
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  Self-Compensated Explosion Pot
  

Plain Explosion Pot
Such a type of explosion Pot is very simple. It is a cylindrical-shaped pot made from insulating material. It includes fixed and moving contact. The moving contact pass through a narrow hole called the throat.
Under fault conditions, the contact separate and arc is struck. The arc vaporizes the oil, producing gas with high pressure. The high pressure compresses the oil to deionize the medium and quench the arc at zero crossings. When the moving contact leaves the pot, cool oil and gas rush through the throat that also helps in quenching the arc.

Plain explosion pot cannot be used for very low or very high currents. as the pressure is directly proportional to the arc current, low current produces very low pressure which may not be enough to quench the arc in time thus increasing the arcing time. on the other hand, a very high arc current may produce very high pressure that can explode the pot. Therefore, such an explosion pot is used for medium current.

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