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

Forced Blast Oil Circuit Breaker
In a force blast oil circuit breaker, the necessary pressure generated for arc quenching does not depend on the internal means (arc current) but it is generated by external means. A mechanical piston that is coupled with the movement of the moving contact presses against the oil to increase its pressure. it safely quenches the arc irrespective of the arc current.
Therefore, force-blast OCB has no limitation like self-blast OCB because it does not depend on the arc current. It can safely extinguish low, medium and high arc currents.
Based on the breaking of the current-carrying contacts, BOCB is divided into two types

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  Single Break Bulk Oil Circuit Breaker
  
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  Double Break Bulk Oil Circuit Breaker
  

Single Break Bulk Oil Circuit Breaker
As the name suggests, such BOCB has only one break between the current-carrying contacts. There is only one fixed contact and one moving contact as shown in the figure. The arc control OCB has a single break OCB design. Upon fault condition, such breakers generate a single arc. Since arc control OCB depends on the pressure generated by the heat of the arc, a single arc generates much more heat and high pressure to deionize the medium.

Double Break Bulk Oil Circuit Breaker
Double break OCB has two breaks between its current-carrying contacts when it opens. There are two fixed contacts and one moving contact. When it separates, two arcs at both ends of the contacts are generated. It lengthens the arc but decreases the heat produced by the arc at one spot.

Plain-Break OCB has a double-break design because it quenches the arc by lengthening the arc and double-break design offers that by breaking the arc into two.
Advantages

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  The oil used for arc quenching has very high dielectric strength
  
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  The oil insulates the live contacts from the earthed parts
  
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  The oil produces hydrogen gas with the heat from the arc which is beneficial for arc quenching.
  
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  The pressure of oil compresses the gas to deionize the medium.
  
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  The gas also helps in cooling the medium.
  

Disadvantages

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  The oil is inflammable and causes a fire hazard.
  
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  The contacts can get damaged with the arc.
  
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  The carbonization of the oil from the contacts reduces its dielectric strength.
  
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  The contacts and the oil must be checked and maintained regularly.
  
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  The use of a huge amount of oil increases its cost
  
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  Their large oil-filled tanks are heavy and take large space.