Introduction to Circuit Breaker

•A circuit breaker is a circuit protection device that, like a fuse, will stop current in the circuit if there is a direct short, excessive current, or excessive heat. Unlike a fuse, a circuit breaker is reusable.

•The circuit breaker does not have to be replaced after it has opened or broken the circuit. Instead of replacing the circuit breaker, you reset it.

•Circuit breakers can also be used as circuit control devices. By manually opening and closing the contacts of a circuit breaker, you can switch the power on and off. Circuit control devices will be covered in more detail in the next chapter.

•Circuit breakers are available in a great variety of sizes and types. It would not be possible to describe every type of circuit breaker in use today, but this chapter will describe the basic types of circuit breakers and their operational principles.

The modern power system deals with huge power network and huge numbers of associated electrical equipment. During short circuit fault or any other types of electrical fault these equipment as well as the power network suffer a high stress of fault current in them which may damage the equipment and networks permanently. For saving these equipments and the power networks the fault current should be cleared from the system as quickly as possible

•Again after the fault is cleared, the system must come to its normal working condition as soon as possible for supplying reliable quality power to the receiving ends. In addition to that for proper controlling of power system, different switching operations are required to be performed.

•So for timely disconnecting and reconnecting different parts of power system network for protection and control, there must be some special type of switching devices which can be operated safely under huge current carrying condition 

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During interruption of huge current, there would be large arcing in between switching contacts, so care should be taken to quench these arcs in safe manner. The circuit breaker is the special device which does all the required switching operations during current carrying condition 

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