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For other uses, see Circuit breaker (disambiguation).
A 2 pole miniature circuit breaker
A 2 pole miniature circuit breaker

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. A switch is a mechanical device used to connect and disconnect an electric Circuit at will An electrical network is an interconnection of Electrical elements such as Resistors Inductors Capacitors Transmission lines Voltage In Electricity supply, overcurrent or excess current is a situation where a larger than intended Electric current exists through a conductor leading to Short Circuit is a 1986 comedy Science fiction film starring Ally Sheedy and Steve Guttenberg and directed by Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. In Electronics and Electrical engineering a fuse (short for fusible link) is a type of Overcurrent protection device Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. The term switchgear, used in association with the electric power system or grid refers to the combination of electrical disconnects fuses and/or Circuit breakers

Contents

Operation

All circuit breakers have common features in their operation, although details vary substantially depending on the voltage class, current rating and type of the circuit breaker.

The circuit breaker must detect a fault condition; in low-voltage circuit breakers this is usually done within the breaker enclosure. Circuit breakers for large currents or high voltages are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism. A relay is an electrical Switch that opens and closes under the control of another Electrical circuit. The trip solenoid that releases the latch is usually energized by a separate battery, although some high-voltage circuit breakers are self-contained with current transformers, protection relays, and an internal control power source.

Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some mechanically stored energy within the breaker is used to separate the contacts, although some of the energy required may be obtained from the fault current itself. The stored energy may be in the form of springs or compressed air. Small circuit breakers may be manually operated; larger units have solenoids to trip the mechanism, and electric motors to restore energy to the springs. A solenoid is a three-dimensional Coil. In Physics, the term solenoid refers to a loop of wire often wrapped around a Metallic core which

The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting the circuit. Contacts are made of copper or copper alloys, silver alloys, and other materials. Service life of the contacts is limited by the erosion due to interrupting the arc. Miniature circuit breakers are usually discarded when the contacts are worn, but power circuit breakers and high-voltage circuit breakers have replaceable contacts.

When a current is interrupted, an arc is generated - this arc must be contained, cooled, and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit. An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive Different circuit breakers use vacuum, air, insulating gas, or oil as the medium in which the arc forms. Different techniques are used to extingish the arc including:

Finally, once the fault condition has been cleared, the contacts must again be closed to restore power to the interrupted circuit.


Arc interruption

Miniature low-voltage circuit breakers use air alone to extinguish the arc. Larger ratings will have metal plates or non-metallic arc chutes to divide and cool the arc. Magnetic blowout coils deflect the arc into the arc chute. In semiconductor testing, contactor can also refer to the specialised socket that connects the Device under test.

In larger ratings, oil circuit breakers rely upon vaporisation of some of the oil to blast a jet of oil through the arc. [1]

Gas (usually sulfur hexafluoride) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the sulfur hexafluoride (SF6) to quench the stretched arc. Sulfur hexafluoride is an Inorganic compound with the formula.

Vacuum circuit breakers have minimal arcing (as there is nothing to ionise other than the contact material), so the arc quenches when it is stretched a very small amount (<2-3 mm). Vacuum circuit breakers are frequently used in modern medium-voltage switchgear to 35,000 volts.

Air circuit breakers may use compressed air to blow out the arc, or alternatively, the contacts are rapidly swung into a small sealed chamber, the escaping of the displaced air thus blowing out the arc.

Circuit breakers are usually able to terminate all current very quickly: typically the arc is extinguished between 30 ms and 150 ms after the mechanism has been tripped, depending upon age and construction of the device.

Short circuit current

Circuit breakers are rated both by the normal current that are expected to carry, and the maximum short-circuit current that they can safely interrupt.

Under short-circuit conditions, a current many times greater than normal can flow (see maximum prospective short circuit current). When electrical contacts open to interrupt a large current, there is a tendency for an arc to form between the opened contacts, which would allow the flow of current to continue. An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive Therefore, circuit breakers must incorporate various features to divide and extinguish the arc.

The maximum short-circuit current that a breaker can interrupt is determined by testing. Application of a breaker in a circuit with a prospective short-circuit current higher than the breaker's interrupting capacity rating may result in failure of the breaker to safely interrupt a fault. In a worst-case scenario the breaker may successfully interrupt the fault, only to explode when reset, injuring the technician.

Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity to use at a panelboard - these circuit breakers are called "supplemental circuit protectors" to distinguish them from distribution-type circuit breakers.


Types of circuit breaker

Front panel of a 1250 A air circuit breaker manufactured by ABB. This low voltage power circuit breaker can be withdrawn from its housing for servicing. Trip characteristics are configurable via DIP switches on the front panel.
Front panel of a 1250 A air circuit breaker manufactured by ABB. This low voltage power circuit breaker can be withdrawn from its housing for servicing. Trip characteristics are configurable via DIP switches on the front panel. A DIP switch is a set of manual electric switches that are packaged in a group in a standard Dual in-line package (DIP (the whole package unit may also be referred

Many different classifications of circuit breakers can be made, based on their features such as voltage class, construction type, interrupting type, and structural features.

Low voltage (less than 1000 VAC) types are common in domestic, commercial and industrial application, include:

The characteristics of LV circuit breakers are given by international standards such as IEC 947. These circuit breakers are often installed in draw-out enclosures that allow removal and interchange without dismantling the switchgear.

Large low-voltage molded case and power circuit breakers may have electrical motor operators, allowing them to be tripped (opened) and closed under remote control. These may form part of an automatic transfer switch system for standby power. Transfer switches allow switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems

Low-voltage circuit breakers are also made for direct-current (DC) applications, for example DC supplied for subway lines. Special breakers are required for direct current because the arc does not have a natural tendancy to go out on each half cycle as for alternating current. A direct current circuit breaker will have blow-out coils which generate a magnetic field that rapidly stretches the arc when interrupting direct current.

Medium-voltage circuit breakers rated between 1 and 72 kV may be assembled into metal-enclosed switchgear line ups for indoor use, or may be individual components installed outdoors in a substation. Air-break circuit breakers replaced oil-filled units for indoor applications, but are now themselves being replaced by vacuum circuit breakers (up to about 35 kV). Like the high voltage circuit breakers described below, these are also operated by current sensing protective relays operated through current transformers. A relay is an electrical Switch that opens and closes under the control of another Electrical circuit. A current transformer ( CT) is a type of instrument Transformer designed to provide a current in its secondary winding proportional to the alternating current The characteristics of MV breakers are given by international standards such as IEC 62271.

Electric power systems require the breaking of higher currents at higher voltages. High-voltage breakers may be free-standing outdoor equipment or a component of a gas-insulated switchgear line-up. Examples of high-voltage AC circuit breakers are:

Low voltage circuit breakers

Photo of inside of a circuit breaker
Photo of inside of a circuit breaker

Small circuit breakers are either installed directly in equipment, or are arranged in a breaker panel. A distribution board divides the electrical mains feed into various circuits providing a fuse or Circuit breaker for each circuit

The 10 ampere DIN rail mounted thermal-magnetic miniature circuit breaker is the most common style in modern domestic consumer units and commercial electrical distribution boards throughout Europe. A DIN rail or top-hat rail is a standardized 35 mm wide metal rail with hat-shaped cross section A consumer unit is a box of fuses or breakers, usually arranged in a single row A distribution board divides the electrical mains feed into various circuits providing a fuse or Circuit breaker for each circuit The design includes the following components:

  1. Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the on position. This is sometimes referred to as "free trip" or "positive trip" operation.
  2. Actuator mechanism - forces the contacts together or apart.
  3. Contacts - Allow current to flow when touching and break the flow of current when moved apart.
  4. Terminals
  5. Bimetallic strip
  6. Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly. A screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw Manufacturing (from Latin manu factura, "making by hand" is the use of tools and labor to make things for use or sale
  7. Solenoid
  8. Arc divider / extinguisher

Magnetic circuit breaker

Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases with the current. A solenoid is a three-dimensional Coil. In Physics, the term solenoid refers to a loop of wire often wrapped around a Metallic core which An electromagnet is a type of Magnet in which the Magnetic field is produced by the flow of an electric current. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. The circuit breaker contacts are held closed by a latch. As the current in the solenoid increases beyond the rating of the circuit breaker, the solenoid's pull releases the latch which then allows the contacts to open by spring action. Some types of magnetic breakers incorporate a hydraulic time delay feature using a viscous fluid. The core is restrained by a spring until the current exceeds the breaker rating. During an overload, the speed of the solenoid motion is restricted by the fluid. The delay permits brief current surges beyond normal running current for motor starting, energizing equipment, etc. Short circuit currents provide sufficient solenoid force to release the latch regardless of core position thus bypassing the delay feature. Ambient temperature affects the time delay but does not affect the current rating of a magnetic breaker.


Thermomagnetic circuit breaker

Thermomagnetic circuit breakers, which are the type found in most distribution boards, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. A distribution board divides the electrical mains feed into various circuits providing a fuse or Circuit breaker for each circuit

Rated current

Circuit breakers are rated both by the normal current that are expected to carry, and the maximum short-circuit current that they can safely interrupt.

Under short-circuit conditions, a current many times greater than normal can flow (see maximum prospective short circuit current). When electrical contacts open to interrupt a large current, there is a tendency for an arc to form between the opened contacts, which would allow the flow of current to continue. An electric arc is an Electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive Therefore, circuit breakers must incorporate various features to divide and extinguish the arc. In air-insulated and miniature breakers an arc chute structure consisting (often) of metal plates or ceramic ridges cools the arc, and magnetic blowout coils deflect the arc into the arc chute. In semiconductor testing, contactor can also refer to the specialised socket that connects the Device under test. Larger circuit breakers such as those used in electrical power distribution may use vacuum, an inert gas such as sulphur hexafluoride or have contacts immersed in oil to suppress the arc. Electricity distribution is the penultimate stage in the delivery (before retail) of Electricity to end users This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. In English to be inert is to be in a state of doing little or nothing This page is about the physical properties of gas as a state of matter Sulfur hexafluoride is an Inorganic compound with the formula. An oil is a substance that is in a viscous Liquid state ( "oily") at ambient temperatures or slightly warmer and is

The maximum short-circuit current that a breaker can interrupt is determined by testing. Application of a breaker in a circuit with a prospective short-circuit current higher than the breaker's interrupting capacity rating may result in failure of the breaker to safely interrupt a fault. In a worst-case scenario the breaker may successfully interrupt the fault, only to explode when reset, injuring the technician.

International Standard IEC 60898-1 and European Standard EN 60898-1 define the rated current In of a circuit breaker for low voltage distribution applications as the current that the breaker is designed to carry continuously (at an ambient air temperature of 30 °C). International standards are Standards developed by international Standards organisations International standards are available for consideration and use worldwide European Committee for Standardization or Comité Européen de Normalisation ( CEN) is a private non-profit organisation whose mission is to foster the European economy The commonly-available preferred values for the rated current are 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A and 100 A[2] (Renard series, slightly modified to include current limit of British BS 1363 sockets). In Industrial design, product developers must choose numerous lengths distances diameters volumes and other characteristic quantities. British Standard BS 1363 specifies the type of Domestic AC power plugs and sockets most commonly used in the United Kingdom, Cyprus, Ireland The circuit breaker is labeled with the rated current in ampere, but without the unit symbol "A". The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second Instead, the ampere figure is preceded by a letter "B", "C" or "D" that indicates the instantaneous tripping current, that is the minimum value of current that causes the circuit-breaker to trip without intentional time delay (i. e. , in less than 100 ms), expressed in terms of In:

Type Instantaneous tripping current
B above 3 In up to and including 5 In
C above 5 In up to and including 10 In
D above 10 In up to and including 20 In
K above 8 In up to and including 12 In

For the protection of loads that cause frequent short duration (approximately 400 ms to 2 s) current peaks in normal operation.

Z above 2 In up to and including 3 In for periods in the order of tens of seconds.

For the protection of loads such as semiconductor devices or measuring circuits using current transformers.

Common trip breakers

Three pole common trip breaker for supplying a three-phase device. This breaker has a 2 A rating
Three pole common trip breaker for supplying a three-phase device. This breaker has a 2 A rating

When supplying a branch circuit with more than one live conductor, each live conductor must be protected by a breaker pole. To ensure that all live conductors are interrupted when any pole trips, a "common trip" breaker must be used. These may either contain two or three tripping mechanisms within one case, or for small breakers, may externally tie the poles together via their operating handles. Two pole common trip breakers are common on 120/240 volt systems where 240 volt loads (including major appliances or further distribution boards) span the two live wires. Refrigerator1svg|left|100px]]A major appliance, or domestic appliance, is usually defined as a large Machine which accomplishes some routine housekeeping task which Three pole common trip breakers are typically used to supply three phase power to large motors or further distribution boards. This article deals with where how and why "three phase" is used

High-voltage circuit breakers

A 1200 A 3-pole 115,000 V breaker at a generating station in Manitoba, Canada.
A 1200 A 3-pole 115,000 V breaker at a generating station in Manitoba, Canada.

Electrical power transmission networks are protected and controlled by high-voltage breakers. Power transmission is the movement of Energy from its place of generation to a location where it is applied to performing useful work. The definition of "high voltage" varies but in power transmission work is usually thought to be 72,500 V or higher, according to a recent definition by the International Electrotechnical Commission (IEC). The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes High-voltage breakers are nearly always solenoid-operated, with current sensing protective relays operated through current transformers. A solenoid is a three-dimensional Coil. In Physics, the term solenoid refers to a loop of wire often wrapped around a Metallic core which A relay is an electrical Switch that opens and closes under the control of another Electrical circuit. A current transformer ( CT) is a type of instrument Transformer designed to provide a current in its secondary winding proportional to the alternating current In substations the protection relay scheme can be complex, protecting equipment and busses from various types of overload or ground/earth fault. An electrical substation is a subsidiary station of an Electricity generation, transmission and distribution system where Voltage A relay is an electrical Switch that opens and closes under the control of another Electrical circuit.

High-voltage breakers are broadly classified by the medium used to extinguish the arc.

High voltage breakers are routinely available up to 765 kV AC. Sulfur hexafluoride is an Inorganic compound with the formula.

Live tank circuit breakers are where the enclosure that contains the breaking mechanism is at line potential, that is, "Live". Dead tank circuit breaker enclosures are at earth potential.

Interrupting principles for high-voltage circuit-breakers

High-voltage circuit-breakers have greatly changed since they were first introduced about 40 years ago, and several interrupting principles have been developed that have contributed successively to a large reduction of the operating energy. These breakers are available for indoor or outdoor applications, the latter being in the form of breaker poles housed in ceramic insulators mounted on a structure.

Current interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as SF6, having excellent dielectric and arc quenching properties. After contact separation, current is carried through an arc and is interrupted when this arc is cooled by a gas blast of sufficient intensity.

Gas blast applied on the arc must be able to cool it rapidly so that gas temperature between the contacts is reduced from 20,000 K to less than 2000 K in a few hundred microseconds, so that it is able to withstand the transient recovery voltage that is applied across the contacts after current interruption. A transient recovery voltage (or TRV for high-voltage Circuit breakers is the Voltage that appears across the terminals after current interruption Sulphur hexafluoride is generally used in present high-voltage circuit-breakers (of rated voltage higher than 52 kV).

In the 1980s and 1990s, the pressure necessary to blast the arc was generated mostly by gas heating using arc energy. It is now possible to use low energy spring-loaded mechanisms to drive high-voltage circuit-breakers up to 800 kV.

Brief history

The first patents on the use of SF6 as an interrupting medium were filed in Germany in 1938 by Vitaly Grosse (AEG) and independently later in the USA in July 1951 by H. AEG ( Allgemeine Elektrizitäts-Gesellschaft, General Electricity Company) was a German producer of Electronics and electrical equipment J. Lingal, T. E. Browne and A. P. Storm (Westinghouse). Founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The first industrial application of SF6 for current interruption dates back to 1953. High-voltage 15 kV to 161 kV load switches were developed with a breaking capacity of 600 A. The first high-voltage SF6 circuit-breaker built in 1956 by Westinghouse, could interrupt 5 kA under 115 kV, but it had 6 interrupting chambers in series per pole. In 1957, the puffer-type technique was introduced for SF6 circuit breakers where the relative movement of a piston and a cylinder linked to the moving part is used to generate the pressure rise necessary to blast the arc via a nozzle made of insulating material (figure 1). In this technique, the pressure rise is obtained mainly by gas compression. The first high-voltage SF6 circuit-breaker with a high short-circuit current capability was produced by Westinghouse in 1959. This dead tank circuit-breaker could interrupt 41. 8 kA under 138 kV (10,000 MV·A) and 37. 6 kA under 230 kV (15,000 MV·A). This performance were already significant, but the three chambers per pole and the high pressure source needed for the blast (1. 35 MPa) was a constraint that had to be avoided in subsequent developments. The excellent properties of SF6 lead to the fast extension of this technique in the 1970s and to its use for the development of circuit breakers with high interrupting capability, up to 800 kV.

The achievement around 1983 of the first single-break 245 kV and the corresponding 420kV to 550 kV and 800 kV, with respectively 2, 3, and 4 chambers per pole, lead to the dominance of SF6 circuit breakers in the complete range of high voltages.

Several characteristics of SF6 circuit breakers can explain their success:

The reduction in the number of interrupting chambers per pole has led to a considerable simplification of circuit breakers as well as the number of parts and seals required. As a direct consequence, the reliability of circuit breakers improved, as verified later on by CIGRE surveys.

Thermal blast chambers

New types of SF6 breaking chambers, which implement innovative interrupting principles, have been developed over the past 15 years, with the objective of reducing the operating energy of the circuit-breaker. One aim of this evolution was to further increase the reliability by reducing the dynamic forces in the pole. Developments since 1996 have seen the use of the self-blast technique of interruption for SF6 interrupting chambers.

These developments have been facilitated by the progress made in digital simulations that were widely used to optimize the geometry of the interrupting chamber and the linkage between the poles and the mechanism.

This technique has proved to be very efficient and has been widely applied for high voltage circuit breakers up to 550 kV. It has allowed the development of new ranges of circuit breakers operated by low energy spring-operated mechanisms.

The reduction of operating energy was mainly achieved by the lowering energy used for gas compression and by making increased use of arc energy to produce the pressure necessary to quench the arc and obtain current interruption. Low current interruption, up to about 30% of rated short-circuit current, is obtained by a puffer blast.

Self-blast chambers

Further development in the thermal blast technique was made by the introduction of a valve between the expansion and compression volumes. When interrupting low currents the valve opens under the effect of the overpressure generated in the compression volume. The blow-out of the arc is made as in a puffer circuit breaker thanks to the compression of the gas obtained by the piston action. In the case of high currents interruption, the arc energy produces a high overpressure in the expansion volume, which leads to the closure of the valve and thus isolating the expansion volume from the compression volume. The overpressure necessary for breaking is obtained by the optimal use of the thermal effect and of the nozzle clogging effect produced whenever the cross-section of the arc significantly reduces the exhaust of gas in the nozzle. In order to avoid excessive energy consumption by gas compression, a valve is fitted on the piston in order to limit the overpressure in the compression to a value necessary for the interruption of low short circuit currents.

Self-blast circuit breaker chamber (1) closed, (2) interrupting low current, (3) interrupting high current, and (4) open.
Self-blast circuit breaker chamber (1) closed, (2) interrupting low current, (3) interrupting high current, and (4) open.

This technique, known as “self-blast” has now been used extensively since 1996 for the development of many types of interrupting chambers. The increased understanding of arc interruption obtained by digital simulations and validation through breaking tests, contribute to a higher reliability of these self-blast circuit breakers. In addition the reduction in operating energy, allowed by the self blast technique, leads to longer service life.

Double motion of contacts

An important decrease in operating energy can also be obtained by reducing the kinetic energy consumed during the tripping operation. One way is to displace the two arcing contacts in opposite directions so that the arc speed is half that of a conventional layout with a single mobile contact.

The thermal and self blast principles have enabled the use of low energy spring mechanisms for the operation of high voltage circuit breakers. They progressively replaced the puffer technique in the 1980s; first in 72. 5 kV breakers, and then from 145 kV to 800 kV.

Comparison of single motion and double motion techniques

The double motion technique halves the tripping speed of the moving part. In principle, the kinetic energy could be quartered if the total moving mass was not increased. However, as the total moving mass is increased, the practical reduction in kinetic energy is closer to 60%. The total tripping energy also includes the compression energy, which is almost the same for both techniques. Thus, the reduction of the total tripping energy is lower, about 30%, although the exact value depends on the application and the operating mechanism. Depending on the specific case, either the double motion or the single motion technique can be cheaper. Other considerations, such as rationalization of the circuit-breaker range, can also influence the cost.

Thermal blast chamber with arc-assisted opening

In this interruption principle arc energy is used, on the one hand to generate the blast by thermal expansion and, on the other hand, to accelerate the moving part of the circuit breaker when interrupting high currents. The overpressure produced by the arc energy downstream of the interruption zone is applied on an auxiliary piston linked with the moving part. The resulting force accelerates the moving part, thus increasing the energy available for tripping.

With this interrupting principle it is possible, during high-current interruptions, to increase by about 30% the tripping energy delivered by the operating mechanism and to maintain the opening speed independently of the current. It is obviously better suited to circuit-breakers with high breaking currents such as Generator circuit-breakers.

Generator circuit-breakers

Generator circuit-breakers are connected between a generator and the step-up voltage transformer. They are generally used at the outlet of high power generators (100 MVA to 1800 MVA) in order to protect them in a reliable, fast and economic manner. Such circuit breakers must be able to allow the passage of high permanent currents under continuous service (6. 3 kA to 40 kA), and have a high breaking capacity (63 kA to 275 kA). They belong to the medium voltage range, but the TRV withstand capability required by ANSI/IEEE Standard C37. 013 is such that the interrupting principles developed for the high-voltage range must be used. A particular embodiment of the thermal blast technique has been developed and applied to generator circuit-breakers. The self-blast technique described above is also widely used in SF6 generator circuit breakers, in which the contact system is driven by a low-energy, spring-operated mechanism. An example of such a device is shown in the figure below; this circuit breaker is rated for 17. 5 kV and 63 kA.

Generator circuit breaker rated for 17.5 kV and 63 kA
Generator circuit breaker rated for 17. 5 kV and 63 kA

Evolution of tripping energy

The operating energy has been reduced by 5 to 7 times during this period of 27 years. This illustrates well the great progress made in this field of interrupting techniques for high-voltage circuit-breakers.

Future perspectives

In the near future, present interrupting technologies can be applied to circuit-breakers with the higher rated breaking currents (63 kA to 80 kA) required in some networks with increasing power generation.

Self blast or thermal blast circuit breakers are nowadays accepted world wide and they have been in service for high voltage applications for about 15 years, starting with the voltage level of 72. 5 kV. Today this technique is also available for the voltage levels 420/550/800 kV.

Other breakers

The following types are described in separate articles.


References

  1. ^ B. M. Weedy, Electric Power Systems Second Edition, John Wiley and Sons, London, 1972, ISBN 0471924458 pp. 428-430
  2. ^ http://bonle.en.alibaba.com/product/50348671/51680889/Switch/MCB___MCCB.html

External links

Dictionary

circuit breaker

-noun

  1. (electrical engineering) An electrical switch capable of opening and closing an electrical circuit in all operating conditions, including fault situations.
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