circuit breakers

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Circuit Breakers:

Circuit Breakers

What is a circuit breaker?:

What is a circuit breaker? Circuit breaker is an absolutely essential device in the modern world, and one of the most important safety mechanisms in your home. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem. Without circuit breakers (or the alternative, fuses), household electricity would be impractical because of the potential for fires and other mayhem resulting from simple wiring problems and equipment failures.

What is a circuit breaker?:

What is a circuit breaker? circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. 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. 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

What is a circuit breaker?:

What is a circuit breaker? Circuit breakers are mechanical switching devices, capable of making, carrying and breaking currents under normal and abnormal circuit conditions.

Classes of circuit breakers according to media:

Classes of circuit breakers according to media AIR CIRCUIT BREAKERS OIL CIRCUIT BREAKERS GAS CIRCUIT BREAKERS VACCUM CIRCUIT BREAKERS

Classes of circuit breakers according to service:

Classes of circuit breakers according to service INDOOR OUTDOOR

Classes of circuit breakers according to method of operations:

Classes of circuit breakers according to method of operations GRAVITY OPENED GRAVITY CLOSED HORIZONTAL BREAK

Air Circuit Breakers:

Air Circuit Breakers Uses the good insulating and arc-quenching property of dry and clean compressed air. When the circuit breaker opens, the sequence of operation is as follows: Main contacts open first, then the secondary contacts, and lastly the carbon contacts. In this manner the carbon contacts take the most of the arcing, and since carbon is very refractory, the contacts are not damaged very much.

Types of AIR Circuit Breaker:

Types of AIR Circuit Breaker Air-Blast CB - air pressure ranges from 300 to 400 PSI. The continuous current carrying capacity is about 42 kA or higher operating at a nominal rating of 38kV. The arc is blown out with a jet of air that is supplied from a pressure tank. To assist in extinguishing the current, the arc is blown into a set of arc chutes, where it is subdivided into several parts, making the task of extinguishing easier.

Types of AIR Circuit Breaker:

Types of AIR Circuit Breaker Magnetic Air CB - uses a combination of strong magnetic-field (coil or soft-iron plates) with a special arc chute to lengthen the arc until the system voltage cannot maintain the arc circuit any longer. Nominal voltages ranges from less than to equal to 15 KV. The arcs are extinguished by blowing them magnetically into arc chutes where they are lengthened, cooled and interrupted.

Types of AIR Circuit Breaker:

Types of AIR Circuit Breaker Uses either a circuit breaker oil, similar to that of transformer oil Inerteen. Operates at over 362 kV. The oil characteristics have a flash point equal to 133 deg. C, burning point at 148 deg. C, freezing point of -40 deg. C, and a viscosity of 57.

TYPES OF OIL CIRCUIT BREAKER:

TYPES OF OIL CIRCUIT BREAKER Dead Tank - steel tank partially filled with oil with covers carrying porcelain or compensating bushings. Live Tank - mounted on cells or metal enclosures, capable of up to 69kV (frame-mounted) only, greater than 69kV they should be floor-mounted.

GAS CIRCUIT BREAKER:

GAS CIRCUIT BREAKER Uses either sulfur hexaflouride, SF6, a very stable compound, inert up to 500 degrees Centigrade, non-flammable, non-toxic, odorless and colorless. Nominal voltages: 800 kV, continuous current up to 400 amperes, symmetrical interrupting rating up to 63 kA.

TYPES OF GAS CIRCUIT BREAKERS:

TYPES OF GAS CIRCUIT BREAKERS Indoor Design - with a service pressure ranging from 20 PSI to 250 PSI, fit into metal-clad switchgear of the dead-tank design for GIS or outdoor substation arrangement or of live-tank design for outdoor applications.

TYPES OF GAS CIRCUIT BREAKERS:

TYPES OF GAS CIRCUIT BREAKERS Dual Pressure Design - is used to a lesser extent. All systems operate fully independently from the auxiliary gas supply.

TYPES OF GAS CIRCUIT BREAKERS:

TYPES OF GAS CIRCUIT BREAKERS Self-Blast Design - arc energy heats the gas, resulting in a pressure rise in the static volume. This pressure then quenches the arc at an ensuing current. Available on 169 kV, 242kV up to 362 kV ratings.

VACUUM CIRCUIT BREAKERS:

VACUUM CIRCUIT BREAKERS - contacts are mounted on an insulating envelope from which virtually all air has been evacuated. Continuous current rating up to 3000A at 38 kV. Two contacts are mounted on an insulating envelope from which virtually all air has been evacuated. One contact is stationary, the other movable. Vacuum interruption has the inherent advantage of moving a lightweight contact only a very small distance in an almost perfect dielectric medium. This results in safe, quiet, and fast switching or interruption of load or fault currents. The moving contact is opened up to full gap distance by means of the driving mechanism, A metal-vapor arc discharge thus occurs in the contact gap through which the current flows until the next current zero. The arc is quenched at zero current.

CLASSIFICATION BY SERVICE:

CLASSIFICATION BY SERVICE INDOOR - for in-house applications, such as an indoor substation. OUTDOOR - used outside subject to weather conditions.

CLASSIFICATION BY METHOD OF OPERATION:

CLASSIFICATION BY METHOD OF OPERATION Gravity-opened the most common type. The contacts are operated by an insulated rod which projects outside the tank. The contacts fall open due to gravity, and therefore they must be raised when it is desired to close the breaker.

CLASSIFICATION BY METHOD OF OPERATION:

CLASSIFICATION BY METHOD OF OPERATION Gravity-closed The breaker will close under the action of gravity. The terminals are at the bottom of the tanks, the circuit being completed through the contact rods. It is equipped with a set of main contacts located at the top of the tanks. These contacts open before the arcing-rod contacts are opened and, hence, are not subjected to arcing and can, therefore, be located outside the tanks. A proper outlet at the top of the tank permits the gases formed due to arcing at the contact to escape.

CLASSIFICATION BY METHOD OF OPERATION:

CLASSIFICATION BY METHOD OF OPERATION Horizontal-break In both the types described above, the circuit is broken by contacts moving in a vertical plane; a third type has its contacts arranged for horizontal motion. The moving contacts can turn through an angle of 90 degrees, thereby obtaining at least two breaking points in the series. For higher voltages it is possible to use a number of contacts in series.

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