Types of Circuit Breaker and Its Importance

In the electrical and electronics world, there are many cases where mishap takes place. It will lead to severe damage to buildings, offices, houses, schools, industries, etc. Trusting voltage and current are not correct, though safety measures are taken. Once circuit breakers are installed it will control the sudden rise of voltage and current. It will help from any accident. Circuit breakers are like the heart of the electrical system. There are different types of circuit breakers where these are installed according to the rating of the system. In house different kind of circuit breaker is used and for industries, another type of circuit breaker is used. Let us discuss the different types of circuit breakers and their importance in detail.

What is a Circuit Breaker?

An electrical circuit breaker is a switching device that can be operated automatically or manually for protecting and controlling the electrical power system. In the modern power system, the design of the circuit breaker has changed depending upon the huge currents and to prevent from the arc while operating.


Circuit Breaker
Circuit Breaker

The electricity that is coming to the houses or offices or schools or industries or any other places from the power distribution grids forms a large circuit. Those lines which are connected to the power plant forming at one end are called the hot wire and the other lines connecting to the ground forming another end. Whenever the electrical charge flows between these two lines it develops potential between them. For the complete circuit, the connection of loads (appliances) offers resistance to the flow of charge and the whole electrical system inside the house or industries will work smoothly.

They work smoothly as long as the appliances have sufficiently resistant and do not cause any over current or voltage. The reasons for heating the wires are too much charge flowing through the circuit or short-circuiting or sudden connection of the hot end wire to the ground wire would heat the wires, causing a fire. The circuit breaker will prevent such situations which simply cut off the remaining circuit.

Different Types of Circuit Breakers

The different types of high voltage circuit breakers which include the following

  • Air Circuit Breaker
  • SF6 Circuit Breaker
  • Vacuum Circuit Breaker
  • Oil Circuit Breaker
  • Air Circuit Breaker

Air Circuit Breaker

This circuit breaker will operate in the air; the quenching medium is an Arc at atmospheric pressure. In many of the countries, the air circuit breaker is replaced by an oil circuit breaker. About the oil circuit breaker, we will discuss later in the article. Thus the importance of ACB is still a preferable choice to use an Air circuit breaker up to 15KV. This is because; oil circuit breaker may catch fire when used at 15V

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The two types of air circuit breakers are

  • Plain air circuit breaker
  • Airblast Circuit Breaker

Plain Air Circuit Breaker

A plain air circuit breaker is also called a Cross-Blast Circuit Breaker. In this, the circuit breaker is fitted with a chamber that surrounds the contacts. This chamber is known as arc chute.

Plain Air Circuit Breaker
Plain Air Circuit Breaker

This arc is made to drive in it. In achieving the cooling of the air circuit breaker, an arc chute will help. From the refractory material, an arc chute is made. The internal walls of arc chute are shaped in such a way that arc is not forced into proximity. It will drive into the winding channel projected on an arc chute wall.

The arc chute will have many small compartments and has many divisions which are metallic separated plates. Here each of small compartments behaves as a mini-arc chute and metallic separation plate act like arc splitters. All arc voltages will be higher than the system voltage when the arc will split into a series of arcs. It is only preferable for low voltage applications.

Air Blast Circuit Breaker

Airblast circuit breakers are used for a system voltage of 245 kV, 420 KV and also even more.Airblast circuit breakers are of two types:

  • Axial blast breaker
  • Axial blast with sliding moving contact.

Axial Blast Breaker

In the axial blaster breaker, the moving contact of the axial blast breaker will be in contact. The nozzle orifice is fixed to the contact of a breaker at a normally closed condition. A fault occurs when high pressure is introduced into the chamber. Voltage is sufficient to sustain high-pressure air when flowed through the nozzle orifice.

Axial Blast Circuit breaker
Axial Blast Circuit breaker
Advantages of Air-Blast Circuit Beaker
  • It is used where frequent operation is required because of lesser arc energy.
  • It is risk-free from fire.
  • Small in size.
  • It requires less maintenance.
  • Arc quenching is much faster
  • The speed of the circuit breaker is much higher.
  • The time duration of the arc is the same for all values of current.
Disadvantages of Air-Blast Circuit Breaker
  • It requires additional maintenance.
  • The air has relatively lower arc extinguishing properties
  • It contains a high capacity air compressor.
  • From the air pipe junction, there may be a chance of air pressure leakage
  • There is the chance of a high rate rise of re-striking current and voltage chopping.

Application and Uses of Air Circuit Breaker

  • It is used for protection of plants, electrical machines, transformers, capacitors, and generators
  • An air circuit breaker is also used in the Electricity sharing system and GND about 15Kv
  • Also used in Low as well as High Currents and voltage applications.

SF6 Circuit Breaker

In the SF6 circuit breaker, the current-carrying contacts operate in sulfur hexafluoride gas is known as an SF6 circuit breaker. It is an excellent insulating property and high electro-negativity. It can be understood that, the high affinity of absorbing free electron. The negative ion is formed when a free electron collides with the SF6 gas molecule; it is absorbed by that gas molecule. The two different ways of attachment of electron with SF6 gas molecules are

SF6 + e = SF6
SF6 + e = SF5- + F

SF6 Circuit Breaker
SF6 Circuit Breaker

The negative ions which are formed will be much heavier than a free electron. Therefore, when compared with other common gases overall mobility of the charged particle in the SF6 gas is much less. The mobility of charged particles is majorly responsible for conducting current through a gas. Hence, for heavier and less mobile charged particles in SF6 gas, it acquires very high dielectric strength. This gas good heat transfer property because of low gaseous viscosity. SF6 is 100 times more effective in arc quenching media than an air circuit breaker. It is used for both medium and high voltage electrical power system from 33KV to 800KV.

Types of SF6 Circuit Breaker

  • Single interrupter SF6 circuit breaker applied up to 220
  • Two interrupters SF6 circuit breaker applied up to 400
  • Four interrupters SF6 circuit breaker applied up to 715V

Vacuum Circuit Breaker

A Vacuum circuit breaker is a circuit in which a vacuum is used to extinct the arc. It has dielectric recovery character, excellent interruption, and can interrupt the high-frequency current which results from arc instability, superimposed on the line frequency current.

Vacuum Circuit Breaker
Vacuum Circuit Breaker

The principle of operation of VCB will have two contacts called electrodes will remain closed under normal operating conditions. Suppose when a fault occurs in any part of the system, then the trip coil of the circuit breaker gets energized and finally, the contact gets separated.

The moment contacts of the breaker are opened in a vacuum, i.e. 10-7 to 10-5 Torr an arc is produced between the contacts by the ionization of metal vapors of contacts. Here the arc quickly gets extinguished, this happens because the electrons, metallic vapors, and ions produced during the arc, condense quickly on the surface of the CB contacts, resulting in quick recovery of dielectric strength.

Advantages

  • VCBs are reliable, compact and long life
  • They can interrupt any fault current.
  • There will be no fire hazards.
  • No noise is produced
  • It has a higher dielectric strength.
  • It requires less power for control operation.

Oil Circuit Breaker

In this type of circuit, breaker oil is used, but mineral oil is preferable. It acts better insulating property than air. The moving contact and fixed contact are immersed inside the insulating oil. When the separation of current takes place, then carrier contacts in the oil, the arc in the circuit breaker is initialized at the moment of separation of contacts, and because of this arc in the oil is vaporized and decomposed in hydrogen gas and finally creates a hydrogen bubble around the arc.

This highly compressed gas bubble around and arc prevents re-striking of the arc after the current reaches zero crossings of the cycle. The OCB is the oldest type of circuit breakers.

Different types of Oil Circuit Breaker

  • Bulk oil circuit breaker
  • Minimum oil circuit breaker

Bulk Oil Circuit Breaker (BOCB)

In the BOCB, oil is used to arc the quenching media and also for insulating media in between earth parts of circuit breaker and current-carrying contacts. The same transformer insulating oil is used.

The working principle of the BOCB says when the current-carrying contacts in the oil are separated, then an arc is generated between the separated contacts. The arc which is established will produce rapidly growing gas bubble around the arc. The moving contacts will move away from the fixed contact of arc and this result the resistance of the arc gets increased. Here the increased resistance will cause lowering the temperature. Hence the reduced formations of gasses surround the arc.

BOCB Circuit breaker
BOB Circuit Breaker

When the current passes through zero-crossing the arc quenching in the BOCB takes place. In the totally airtight vessel, the gas bubble is enclosed inside the oil. The oil will surround with high pressure on the bubble, this results in highly compressed gas around the arc. When the pressure is increased the deionization of the gas also increases, which results in arc quenching. The hydrogen gas will help in cooling the arc quenching in the oil circuit breaker.

Advantages
  • Good cooling property because of decomposition
  • Oil has high dielectric strength
  • It acts as an insulator between earth and live parts.
  • The oil used here will absorb arc energy while decomposing
Disadvantages
  • It will not permit high speed of interruption
  • It takes a long arcing time.

Minimum Oil Circuit Breaker

It is a circuit breaker that utilizes oil as the interrupting media. The minimum oil circuit breaker will place the interrupting unit in an insulating chamber at the live potential. But insulating material is available in the interrupting chamber. It requires less amount of oil so it is called a minimum oil circuit breaker.

Minimum Oil Circuit Breaker
Minimum Oil Circuit Breaker
Advantages
  • It requires less maintenance.
  • It is suitable for both automatic operation and manual.
  • It requires a smaller space
  • The cost of breaking capacity in MVA is also less.
Disadvantages
  • Oil deteriorates because of carbonization.
  • There is a possibility of explosion and fire
  • As it has a smaller quantity of oil, so carbonization increases.
  • It is very difficult to remove gases from the space between the contacts.

In this article, the different types of circuit breakers, i.e. Air Circuit Breaker, SF6 Circuit Breaker, Vacuum Circuit Breaker, and Oil Circuit Breaker have been discussed in a short detailed just to understand the basic concept about these circuit breakers. And their subdivision is also discussed along with advantages and disadvantages. We have discussed every concept very clearly. If you have not understood any of the topics, you feel any information is missing or to implement any electrical projects for engineering students, please feel free to comment in the below section.

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4 Comments

    1. Tarun Agarwal says:

      Hi Dip
      There are several types of circuit breakers based on application low voltage, high voltage, air, oil, vacuum, MCCB, single pole, etc.

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