Oil Circuit Breaker( Types , Advantages and disadvantages) Electronicsinfos

What is Oil Circuit Breaker?

An oil Circuit breaker is a type of breaker in which Oil is used as a medium to provide insulation. There are many types of circuit breakers W.r.t Construction but we discuss two types of oil circuit breakers W.r.t oil filling one is the Low oil circuit breaker and the other is the bulk oil circuit breaker which is defined below. 

Classification Of Circuit Breaker

1. Bulk Oil circuit breaker
2. Low Oil circuit breaker

Bulk Oil circuit breaker

A bulk oil circuit breaker is a type of circuit breaker in which all operating mechanisms and breaker contacts are Immersed in the oil. When contacts are open this oil also provides insulation to current-carrying parts. This type of Braker is used in the power system. when contacts are separate the arc is produced between the contacts. due to the arc, heat is produced and the result is the oil is decomposed into gasses and vapours. the new oil replaces with the vapour oil and stops an arc striking process. When oil is moved in the vapour position some action happens in the oil i.e

• The Mechanical pressure happens in contacts due to the quantity of oil.
• The Mechanical pressure produces due to the Arc current.
• The External Mechanical Pressure.

There are different parts of the oil circuit breaker defined below

• Tank (Boiler Plates)
• Dielectric oil
• Moving Contacts (Copper)
• The gas formed by the decomposition of 2 (Hydrogen 70%)
• Arc Control Device
• Fixed Contacts
• Tension Rods
• Conductor Copper
• Bushing Oil filled 
• Conductor

There are some limitations of the bulk oil circuit breaker is

• More oil quantity is used in the steel tank.
• The Dielectric strength is reduced over time.
• The tank size is large 

Types of bulk Oil C.B W.r.t Construction

Different types of circuit breaker W.r.t Construction are defined below

• Plain break Type O.C.B
• Self-Generated Pressure Type O.C.B 
• Externally Generated Pressure Type O.C.B    

Plain break Type O.C.B

A plain break-type circuit breaker consists of a weather-tight steel tank that protects the circuit breaker from the environment. we fill a mineral oil in tank. The fixed and moving contacts are immersed in the oil. when fixed contact is separate from moving contacts the arc is produced in between them. The heat is produced due to the arc that temperature is reached up to 5000k. This high value of heat affects the oil and vaporizes them. there are different gasses produced i.e hydrogen, Mathene Ethylene etc. These gasses also act as Explosives so The upper part of the tank is a strong sheet.

In normal conditions the fixed contacts and moving contacts are close. when faults occur the moving contacts are separate and the arc is produced between them which changes the oil into hydrogen gas. when contacts are separated the arc length is increased and the change in the ratio of oil to gas is decreased. there are technical problems that occur in the O.C.B. due to gap length so this breaker is not used to handle the high current. This breaker is limited to 150 MVA.there are two types of plain circuit breakers that are described below

• Single break oil C.B
  
• Double Break Oil C.B

Single break oil C.B

Single Break CB is a type of plain oil circuit breaker where the arc is produced on a single bushing side.

Double Break Oil C.B   

A double break oil breaker is a plain oil CB where two arcs are produced on two sides is called double break oil C.B.There are some limitations to a plain oil circuit breaker defined below

Limitations of bulk Oil C.B

• This breaker is not used up to 150 MVA because of its high size.
• This breaker has a long and unreliable arching time.
• This breaker has no fast interruption. 

Advantages of bulk Oil C.B

• The Arc distinguish time as fast. 
• The Gasses which is produced in the oil also provide effective cooling.
•  The Oil provides Good Dielectric properties.
• The Dielectric property minimizes the Arc Restriking.
• The construction of an oil circuit breaker is simple.
• Oil Circuit breakers have a high Rupturing capacity.
• Oil CB is Suitable for manual and Automatic Operations.
• there is space available in the busing to set the C.T.

Disadvantages of bulk Oil C.B

• The Chance of Explosives is Available because of Explosive Gasses produced in the medium.
• They need maintenance regularly.
• The operating cost is high.
• The Efficiency is Affected due to gasses produced in the Tank.
• The Tank size and Waight are large.
• We need Regular checkups to maintain the oil quality and quantity.
• We need expensive heavy mineral oil.
• This is not suitable for outdoor purposes.
• The Wear and tear of contacts are possible.
• We need a high quantity of steel.

Low Oil circuit breaker

A low Oil Circuit breaker is a type of oil circuit breaker in which the minimum or small quantity of oil is used in the tank. The current-carrying parts are insulated with porcelain or any other insulating medium. In the Bulk Oil Circuit breaker, the 10% oil is just used to distinguish the arc. The remaining 90% is used to earth the live parts. There is a small container in the low-oil CB to hold the Oil. The container is supported by a Porcelain insulator that provides enough insulation. Low Oil C.B. needs less space as compared to Bulk Oil C.B. There are different ranges of Low Oil CB available on the market.

Ranges of low Oil C.B

• 3.6KV
•  7.2KV
•  12KV
•  36KV
• 72.5KV
•  145Kv
•  245KV
•  420KV

Construction Of Low oil C.B

There are two compartments in the low-oil C.B. that is filled with Mineral Oil. The upper Chamber is called the circuit chamber and the lower chamber is called the supporting chamber. These two chambers are separated from each other so oil is not entering another compartment. The Circuit Braking Chamber need a Low quantity of oil. The Circuit Braking Chamber consist of the following parts

• Upper and lower fixed contacts
• Moving Contacts
• Turbulator

Advantages Of Low Oil C.B

•  Need a Low quantity of oil to distinguish the arc.
  
•  The Size and weight are small.
•  The cost is low. 
•  suitable for manual and automatic operations.
  
•  The low oil breaker needs less space.

Disadvantages Of Low Oil C.B

• The Lifetime of contacts is small
• The Chance of Explosion is available.
• They need regular maintenance.
• Restocking Action is possible.
• They faced a problem carrying the C.T.
• We need regular oil level checkups.
• The degree of carbonization is high.

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