Classification of Circuit Breakers | Arduino Tricks
Power System

Classification of Circuit Breakers

July 1, 2019



There square measure many ways that of classifying circuit breakers. However, the foremost general approach of classification is on the premise of the medium used for arc extinction. The medium used for arc extinction is typically oil, air, greenhouse gas (SF6) or vacuum. consequently, circuit breakers could also be classified into :

  • Oil circuit breakers
  • Air-blast circuit breakers
  • Sulfur hexafluoride circuit breakers
  • Vacuum circuit breakers

Oil Circuit Breakers:


The contacts square measure opened underneath oil associate degreed an arc is stricken between them. the warmth of the arc evaporates the encircling oil and dissociates it into a considerable volume of gassy gas at high. The gas occupies a volume concerning one thousand-fold that of the oil rotten. The oil is, therefore, pushed removed from the arc associate degreed an increasing gas bubble surrounds the arc region and adjacent parts of the contacts. The arc extinction is expedited in the main by 2 processes.

Firstly, the gas has high heat conduction and cools the arc, therefore aiding the de-ionization of the medium between the contacts. Secondly, the gas sets up turbulence within the oil and forces it into the house between contacts, therefore eliminating the arcing.

Oil Circuit Breaker

The oil circuit breakers find extensive use in the power system. These can be classified into the following types :

  • Bulk oil circuit breakers: which use an outsized amount of oil. The oil should serve 2 functions. Firstly, it extinguishes the arc throughout the gap of contacts and second, it insulates the present conducting components from each other and from the earthed tank. Such circuit breakers are also classified into:
  1. Plain break oil circuit breakers
  2. Arc control oil circuit breakers.
  • Low oil circuit breakers: which use the minimum quantity of oil. In such circuit breakers, oil is employed just for arc extinction; the present conducting components are insulated by air or ceramic ware or organic insulant.

Advantages:

the benefits of oil as associate degree arc conclusion medium square measure:

  1. It absorbs the arc energy to decompose the oil into gases that have wonderful cooling properties.
    products from the arc path.
  2. It acts as associate degree stuff and permits smaller clearance between live conductors and earthed parts.
  3. the encircling oil presents the cooling surface in shut proximity to the arc.

Disadvantages:

The disadvantages of oil as associate degree arc conclusion medium square measure :

  1. it’s flammable and there’s a risk of a fireplace.
  2. it should type associate degree explosive with air
  3. The arcing merchandise (e.g., carbon) stay within the oil and its quality deteriorates with sequential operations. This necessitates periodic checking and replacement of oil.



Plain break oil circuit breakers:


A plain-break oil electrical fuse involves the easy method of separating the contacts beneath the complete of the oil within the tank. there’s no special system for arc management apart from the rise long caused by the separation of contacts. The arc extinction happens once a definite crucial gap between the contacts is reached.

The plain-break oil electrical fuse is that the earliest kind from that all different circuit breakers have developed. it’s an awfully easy construction. It consists of mounted ANd moving contacts clathrate during a sturdy weather-tight earthed tank containing oil up to a definite level and an air cushion higher than the oil level. The air cushion provides enough room to permit for the reception of the arc gases while not the generation of unsafe pressure within the dome of the electrical fuse.

Under traditional operational conditions, the mounted and moving contacts stay closed and also the breaker carries the conventional circuit current. once a fault happens, the moving contacts are forced down by the protecting system ANd an arc is stricken that vapourises the oil principally into chemical element gas. The arc extinction is expedited by the subsequent processes.

Oil Circuit Breaker

Advantages:

  1. The element gas bubble generated around the arc cools the arc column and aids the deionization of the medium between the contacts.
  2. The gas sets up turbulence within the oil and helps in eliminating the arcing merchandise from the arc path.
  3. because the arc lengthens thanks to the separating contacts, the staff strength of the medium is inflated.

The results of these actions are that at some important gap length, the arc is destroyed and also the circuit current is interrupted.

Disadvantages:

  1. there’s no special management over the arc aside from the rise long by separating the moving contacts. Therefore, for the no-hit interruption, long arc length is critical.
  2. These breakers have long and inconsistent arcing times.
  3. These breakers don’t allow high-speed interruption.

thanks to these disadvantages, plain-break oil circuit breakers are used just for low-tension applications wherever high breaking-capacities don’t seem to be vital. it’s a usual observe to use such breakers for low capability installations for voltages, not Olympian eleven potential units.



Arc control oil circuit breakers:


In case of plain-break oil, fuse mentioned higher than, there’s little artificial management over the arc. Therefore, relatively long arc length is important so as that turbulence within the oil caused by the gas might assist in extinction it.

  1. Arc Control Circuit BreakerSelf-blast oil circuit breakers: In this variety of fuse, the gases created throughout the arcing area unit confined to a little volume by the utilization of AN insulating rigid pressure chamber or pot close the contacts. Since the area on the market for the arc, gases are restricted by the chamber, terribly air mass is developed to force the oil and gas through or around the arc to extinguish it. The magnitude of pressure developed depends upon the worth of fault current to be interrupted.
  2. Forced-blast oil circuit breakers: In the self-blast oil circuit breakers mentioned higher than, the arc itself generates the mandatory pressure to force the oil across the arc path. the main limitation of such breakers is that arcing times tend to be long and inconsistent once operational against currents significantly but the rated currents. it’s as a result of the gas generated is far reduced at low values of fault currents.

This problem is overcome in forced-blast oil circuit breakers during which the mandatory pressure is generated by external mechanical means that freelance of the fault currents to be broken. during a forced -blast oil fuse, pressure level is made by the piston-cylinder arrangement. The movement of the piston is automatically coupled to the moving contact. once a fault happens, the contacts get separated by the protecting system ANd an arc is smitten between the contacts.

Air-blast circuit breakers:


These breakers use a hard-hitting air-blast as associate arc extinction medium. The contacts square measure opened in a very flow of air-blast established by the gap of the blast valve. The air-blast cools the arc and sweeps away the racing product to the atmosphere. This chop-chop will increase the material strength of the medium between contacts and prevents from establishing the arc. Consequently, the arc is destroyed and therefore the flow of current is interrupted.

Advantages:

Oil Circuit Breaker

An air-blast breaker has the subsequent blessings over associate oil circuit breaker:

  1. the chance of fireside is eliminated.
  2. The arcing product square measure utterly removed by the blast whereas the oil deteriorates with serial operations; the expense of standard oil replacement is avoided.
  3. the expansion of material strength is therefore fast that final contact gap required for arc extinction is incredibly little. This reduces the scale of the device.
  4. The arcing time is incredibly little thanks to the fast build-up of material strength between contacts. Therefore, the arc energy is merely a fraction of that in oil circuit breakers, therefore leading to less burning of contacts.
  5. thanks to lesser arc energy, air-blast circuit breakers square measure terribly appropriate for conditions wherever frequent operation is needed.
  6. The energy equipped for arc extinction is obtained from hard-hitting air and is freelance of the present to be interrupted.

Disadvantages:

The use of air because the arc extinction medium offers subsequent disadvantages :

  1. The air has comparatively inferior arc ending properties.
  2. The air-blast circuit breakers square measure terribly sensitive to the variations within the rate of rising of restriking voltage.
  3. goodly maintenance is needed for the mechanical device plant that provides the air-blast.
  4. The air blast circuit breakers square measure finding wide applications in high voltage installations.



Sulfur hexafluoride circuit breakers:


In such circuit breakers, fluoride (SF6) gas is employed because of the arc extinction medium. The SF6 is AN electro-negative gas and contains a robust tendency to soak up free electrons. The contacts of the breaker square measure opened {in a|during a|in AN exceedingly|in a very} aggressive flow of SF6 gas and an arc is smitten between them. The conducting free electrons within the arc square measure apace captured by the gas to make comparatively immobile negative ions.

Construction:

It consists of mounted and moving contacts fencelike in an exceeding chamber (called arc interruption chamber) containing SF6 gas. This chamber is connected to the SF6 gas reservoir. once the contacts of the breaker square measure opened, the valve mechanism permits an aggressive SF6 gas from the reservoir to flow towards the arc interruption chamber. The mounted contact may be a hollow cylindrical current carrying contact fitted with AN arc horn. The moving contact is additionally a hollow cylinder with rectangular holes within the sides to allow the SF6 gas to let loose through these holes when flowing on and across the arc.

SF6 Circuit Breaker

Working:

In the closed position of the breaker, the contacts stay encircled by SF6 gas at the pressure of concerning 2·8 kg/cm2 once the breaker operates, the moving contact is force apart ANd an arc is smitten between the contacts. The movement of the moving contact is synchronized with the gap of a valve which allows SF6 gas at fourteen kg/cm2 pressure from the reservoir to the arc interruption chamber. The aggressive flow of SF6 apace absorbs the free electrons within the arc path to make immobile negative ions that square measure ineffective as charge carriers. The result’s that the medium between the contacts quickly build up high insulator strength and cause the extinction of the arc.

Advantages:

Due to the superior arc extinction properties of SF6 gas, the SF6 circuit breakers have several blessings over oil or air circuit breakers. a number of them square measure listed below :

  1. thanks to the superior arc extinction property of SF6, such circuit breakers have terribly short arcing time.
  2. Since the material strength of SF6 gas is two to three times that of air, such breakers will interrupt a lot of larger currents.
  3. The SF6 electrical fuse offers quiet operation thanks to its closed gas circuit and no exhaust to atmosphere, in contrast to the air blast electrical fuse.
  4. The closed gas enclosure keeps the inside dry in order that there’s no wet downside.
  5. there’s no risk of the fireplace in such breakers as a result of SF6 gas is non-inflammable.
  6. There are not any carbon deposits in order that trailing and insulation issues square measure eliminated.
  7. The SF6 breakers have an occasional maintenance value, lightweight foundation needs, and minimum off-line equipment.
  8. Since SF6 breakers square measure whole boxed in and sealed from the atmosphere, they’re notably appropriate wherever explosion hazard exists e.g., coal mines.

Disadvantages:

  1. SF6 breakers square measure expensive thanks to the high value of SF6.
  2. Since SF6 gas has got to be repaired once each operation of the breaker, further instrumentation is needed for this purpose.

Applications:

A typical SF6 electrical fuse consists of device units every capable of handling currents up to sixty Ka and voltages within the vary of 50—80 potential unit. variety of units square measure connected nonparallel consistent with the system voltage. SF6 circuit breakers are developed for voltages a hundred and fifteen potential unit to 230 potential unit, power ratings ten MVA to twenty MVA and interrupting time but three cycles.



Vacuum circuit breakers:


 Since vacuum offers the very best insulating strength, it’s so much superior arc extinguishing properties than the other medium. for instance, once contacts of a breaker square measure opened in a vacuum, the interruption happens initially current zero with stuff strength between the contacts build up at a rate thousands of times over that obtained with different circuit breakers.

Principle:

The production of arc in an exceeding vacuum electrical fuse and its extinction may be explained as follows: once the contacts of the breaker square measure opened in a vacuum, an associate arc is created between the contacts by the ionization of metal vapors of contacts. However, the arc is quickly destroyed as a result of the silver vapors, electrons, and ions created throughout arc speedily condense on the surfaces of the electrical fuse contacts, leading to fast recovery of stuff strength.

Vaccum Circuit Breaker

Construction:

It consists of mounted contact, moving contact and arc protect mounted within a chamber. The movable member is connected to the management mechanism by chrome steel bellows. this allows the permanent protection of the chamber therefore on eliminate the likelihood of a leak. A glass vessel or ceramic vessel is employed because the outer insulating body. The arc protect prevents the deterioration of the interior stuff strength by preventing silver vapors falling on the within the surface of the outer insulating cowl.

Working:

When the breaker operates, the moving contact separates from the mounted contact associated an arc is affected between the contacts. the assembly of the arc is because of the ionization of metal ions and depends pretty much upon the fabric of contacts. The arc is quickly destroyed as a result of the silver vapors, electrons, and ions created throughout arc square measure subtle in an exceedingly short time and taken by the surfaces of moving and glued members and shields.



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