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

Radial Venting MOCB
The radial venting MOCB has multiple vents designed radially along with the arc chamber as suggested by its name. When the arc is stretched between the contacts, the arc is swept radially through the vents. Such design developed low pressure therefore, it is used for high arc current.

A combination of both axial and radial venting arc chambers in MOCB is used for efficiently quenching both low and high arc current.
Oil Impulse Circuit Breaker
The Oil impulse circuit breaker is another type of MOCB that develops pressure by external means. A piston compresses the oil that is released through a jet fixated between the contacts to quench the arc. It uses lesser oil than MOCB. Since the pressure is independent of the arc current, it can be used for low as well as high arc current.
Advantages

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  It requires a very little amount of oil.
  
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  Less amount of oil means the risk of fire hazards is low.
  
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  It has low weight.
  
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  It has small size and takes up small space
  
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  It is cheaper than BOCB.
  
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  It has easier maintenance and oil can be easily replaced.
  
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  Best for installation in places where it is not frequently used.
  

Disadvantages

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  Lesser oil is more affected by the amount of carbonization from the contacts.
  
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  The oil quickly losses its dielectric strength.
  
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  It requires more frequent maintenance.
  

Maintenance of Oil Circuit Breaker
During a fault condition, the arc can damage the contacts and the oil can get carbonized which decreases the dielectric strength of the oil. Consequently, its breaking capacity is reduced and the breaker may fail. Therefore, the contacts, as well as the oil, should be monitored and replaced to maintain its dielectric strength.
Advantages & Disadvantages of of Oil Circuit Breakers
Advantages

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  The oil used is a better arc quenching medium than air.
  
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  The oil used has very high dielectric strength
  
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  The dielectric strength of the oil increase with the increase in pressure.
  
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  The arc energy is utilized to vaporize the oil to increase its pressure.
  
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  The oil is also used as insulation between live and earthed parts.
  
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  The gas vapors also help in cooling the medium.
  
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  Oil circuit breakers are cheaper than other high voltage oil-less circuit breaker
  

Disadvantages

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  The oil is inflammable and can cause fire hazards.
  
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  The oil can get carbonized that reduces its dielectric strength.
  
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  It requires maintenance and replacement of contacts and oil with fresh oil.
  

Applications of Oil Circuit Breaker
The oil circuit breakers are used in high voltage applications such as in power grids, substations, powerlines and transmission and distribution systems for up to 220 kV.