Electrical Circuit Breaker | Operation and Types of Circuit Breaker

Electrical Circuit Breaker | Operation and Types of Circuit Breaker

An electrical breaker may be a switch device that may be damaged manually or mechanically for dominant and supporting the electric power system. except a circuit breaker, there is a high risk of electrical fires, electrocution, and electrical shocks. There are different types of circuit breakers which are founded on voltage, installation location, external design and interrupting mechanism. 

Circuit Breaker

A circuit breaker is a switching device that interrupts the abnormal or faults current. It is a mechanical device that disturbs the stream of high magnitude (fault) current and in additions performs the function of a switch. The circuit breaker is mainly designed for closing or opening of an electrical circuit, thus protects the electrical system from damage.

Working Principle of Circuit Breaker

The circuit breaker mainly builds of fixed contacts and moving contacts. In common “ON” state of the circuit breaker, these two contacts are physically attached to each other due to applied mechanical arc on the moving contacts. There is an arrangement stored potential energy in the operating mechanism of a circuit breaker which is released if the switching signal is given to the breaker. The mechanical energy are often keep within the fuse by varied ways that like by deforming metal spring, by compressed gas, or by hydraulic pressure. But whatever the source of expectation energy, it must be released during operation. The release of potential energy makes the sliding of the moving contact in a speedy manner.

DIFFERENT TYPES OF CIRCUIT BREAKERS

  1. Based on Voltage

    1. Low voltage circuit breakers-These breakers are rated for use at low voltages up to 2 kV and are principally used in small-scale industries.
    2. High voltage circuit breakersThese breakers are rated for behavior at voltages greater than 2 kV. High voltage circuit breakers are therewithal subdivided into transmission class breakers
      • Those which are rated 123 kV and above.
      • Medium voltage class circuit breakers.
  2. By Installation Location

    1. Indoor circuit breakersThese is designed to use inside the buildings or in weather-resistant enclosures. They are typically operated at a medium voltage with a metal-clad switchgear enclosure.
    2. Outdoor Circuit breakersYou can use these breakers outdoors without any ceiling due to their design. Their external perimeter arrangement is strong compared to the indoor breakers and can Counteract wear and tear.
  3. Based on External Design

    1. Dead tank circuit breakersThe breakers whose enclosed tank is at ground potential are known as dead tank circuit breakers. Their tank encloses all the insulating and interrupting medium. In other words, the tank is shorted to ground or it is at dead potential.
    2. Live tank circuit breakersThese breakers have a tank housing interrupter that is at a potential above the ground. It is above the ground with some insulation medium in between.
  4. By Interrupting Mechanism

    1. Air circuit breakerThis breaker uses air as an insulating and interrupting medium. The breaker is sub-classified into two types
      • Low voltage circuit breaker whose value lies under 1000 V
      • High voltage circuit breaker whose value is 1000 V and above. It is whatever classified into oil circuit breakers and the oil-less circuit breaker
    2. Oil circuit breakerIt uses oil as associate degree interrupting and insulating medium. These breakers are divided into 2sorts supported the pressure and quantity of oil used.
    3. Vacuum circuit breakersThese breakers use vacuum because of the interrupting medium because of its high nonconductor and disseminating properties.
    4. MCB (Miniature Circuit Breaker)The current ratings for this breaker area unit but 100A and has only 1 over-current protection designed inside it. The trip settings are not regular in this circuit.
    5. MCCB (Moulded Case Circuit Breakers)Current ratings for these breakers are higher than 1000A. They have earth fault protection along with current protection. The trip settings of the manhandled Case Circuit Breaker can be adjusted easily.
    6. Single pole circuit breakerThis breaker has one hot wire and one neutral wire that operate at 120 V. When there is a fault, it will intermission just the hot wire.
    7. Double pole circuit breakerThis is used for 220 V. There are two hot wires and both the poles need to be interrupted.
    8. GFI or GFCI circuit breaker (Ground fault circuit interrupter)These are safety switches that trip on ground-fault current. The GFCI breaker interrupts the electrical circuit when it detects the slightest variance between phase and neutral wires.
    9. Arc Fault circuit interrupter (AFCI)-The AFCI breaker interrupts the circuit during excessive arc conditions and prevents fire. Under the common arcing condition, this breaker will be idle and won’t interrupt the circuit.

It is absolutely critical that circuit breakers are a part of every home to protect the families residing within.

Three Reasons Why Circuit Breaker Keep Tripping

circuit breaker

  1. Circuit Overloads A circuit overload is one of the main reasons why circuit breakers trip every moment. This occurs when you want an individual circuit to provide more electricity than its actual capacity. This will lead to the overheating of the circuit which puts all the electrical machinery connected to the circuit at risk. For example, if your television is connected to the circuit which in reality needs 15 amps but is now using 20 amps, then the circuit of the television system will get fried and harmed. The circuit breaker trips to prevent this from happening, potentially even preventing a major fire. You can address this problem by trying to redistribute your electrical devices and keeping them off of the same circuits. You can even turn off some devices to minimize the electrical load on the circuit breaker.
  2. Short Circuits Another common reason why circuit breakers trip is a short circuit, which is more dangerous than an overloaded circuit. A short circuit is involving when a “hot” wire comes into contact with a “neutral wire” in one of your electrical outlets. Whenever this happens, a large amount of current will flow through the circuit, creating more heat than what the circuit can handle. When this happens the breaker will trip, shutting off the circuit to besiege dangerous events such as a fire. Short circuits could occur for a number of reasons such as faulty wiring or a loose connection You can identify a short circuit by a burning smell that is usually left around the breaker. Additionally, you may also notice a brown or black discoloration around it. 
  3. Ground Fault Surges Ground fault surges are like to short circuits. They occur when a hot wire touches a ground wire that is made of bare copper or the side of a metal outlet box which is connected to the ground wire. This will reason more electricity to pass through it which the circuit cannot handle. The breaker trips in order to protect the circuit and machinery from overheating or from potential fires. If ground fault surges occur, you can identify them through a decolorization around your outlet. If you avoid or overlook any of these problems, you are putting the safety of your home and loved ones at great risk. If you experience tripping of the circuit breakers quite frequently, it is time to call in the professionals to inquire into the problem. Do not try to handle this issue on your own.

 

Types of Circuit Breaker

Circuit breakers are principally classified on the basis of rated voltages. Circuit breakers under rated voltage of 1000V are known as the low voltage circuit breakers and above 1000V are called the high voltage circuit breakers. The most common way of the classification of the circuit breaker is on the basis of the medium of arc extinction. Such types of circuit breakers are as follows:-

  1. Oil Circuit Breaker
    • Bulk Oil Circuit Breaker
    • Minimum Oil Circuit Breaker
  2. Minimum Circuit Breaker
  3.  Air Blast Circuit Breaker
  4.  Sulphur Hexafluoride Circuit Breaker
  5.  Vacuum Circuit Breaker
  6.  Air Break Circuit Breaker

Oil Circuit Breaker

Mineral oil has better insulating substance than air. In oil circuit breaker the fixed contact and moving contact are dipped inside the insulating oil. whensoever there is a separation of current carrying contacts in the oil, the arc in circuit breaker is initialized at the jiffy of separation of contacts, and due to this arc, the oil is vaporized and decomposed in in most cases hydrogen gas and ultimately creates a hydrogen bubble around the arc. This highly compressed gas bubble around the arc prevents re-striking of the arc after current reaches zero crossings of the cycle. The oil circuit breaker is one of the ancient types of circuit breakers.circuit breaker

Operation of Oil Circuit Breaker

The operation of the oil circuit breaker is quite simple to let’s have a discussion. When the current-carrying contacts in the oil are separated an arc is founded in between the separated contacts. In reality, when the separation of contacts has just started, the distance between the current contacts is small as a result the voltage gradient between contacts becomes high. This high voltage gradient between the contacts ionized the oil and consequently starts arcing between the contacts. This arc will generate a large amount of heat in surrounding oil and vaporizes the oil and decomposes the oil in mostly hydrogen and a small amount of methane, ethylene, and acetylene. The hydrogen gas cannot remain in molecular form and it is broken into its atomic form releasing a lot of heat. The arc temperature may reach up to 5000oK. Due to this high temperature, the gas is freed surround the arc very rapidly and forms an excessively fast-growing gas bubble around the arc. It is established that the mixture of gases seize a volume about one thousand times that of the oil decomposed.  we can assume how quick the gas bubble around the arc will grow in size. If this growing gas bubble around the arc is shrunk by any means then the rate of deionization process of ionized gaseous media in among the contacts will accelerate which rapidly increase the dielectric strength between the contacts and consequently the arc will be quenched at zero crossings of the current cycle. This is the basic operation of the oil circuit breaker. In addition to that cooling effect of hydrogen gas surround the arc path also aid, the quick arc quenching in oil circuit breaker.

Types of Oil Circuit Breakers

There are mainly two types of oil circuit breakers available-

Bulk Oil Circuit Breaker 

The bulk oil circuit breaker or BOCB is such types of circuit breakers where oil is used as arc quenching media as well as insulating media among current carrying contacts and earthed parts of the breaker. The oil used here is the same as the transformer insulating oil.

Minimum Oil Circuit Breaker or MOCB

These types of circuit breakers take advantage of oil as the interrupting media. However, unlike bulk oil circuit breaker, a minimum oil circuit breaker places the interrupting unit in the insulating chamber at the live potential. The insulating oil is available only in the interrupting chamber. The features of designing MOCB are to reduce the requirement of oil, and hence these breakers are called minimum oil circuit breaker.

Advantages of Oil as an Arc Quenching

  1. The oil has high dielectric strength and provides insulation between the contact after the arc has been extinguished.
  2. The oil used in circuit breaker provides small decontamination between the conductors and the earth components.
  3. The hydrogen gas is made in the tank which has a high diffusion rate and good cooling properties.

Disadvantages of Oil as an Arc Quenching

  1. The oil used in oil circuit breaker is combustible and hence, cause a fire hazard.
  2. There is a risk of formation of the explosive mixture with air.
  3. Due to decomposition of oil in the arc, the carbon particles are generated which polluted the oil and hence the dielectric strength of the oil decreases.

Maintenance of oil circuit breaker

After a circuit breaker has cut by short-circuit current, sometimes their contacts may get burnt due to arcing. Also, the dielectric oil gets carbonized in the area of the contacts, thereby losing its dielectric strength. This results in the waned breaking capacity of the breaker. Therefore, the maintenance of the oil circuit breaker is indispensable for checking and replacement of oil and contacts.

 

Summary
Electrical Circuit Breaker | Operation and Types of Circuit Breaker
Article Name
Electrical Circuit Breaker | Operation and Types of Circuit Breaker
Description
A circuit breaker is a switching device that interrupts the abnormal or faults current. It is a mechanical device that disturbs the stream of high magnitude (fault) current and in additions performs the function of a switch.
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Publisher Name
Habib
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