What is Circuit Breaker?
Definition of circuit breaker : -
Electrical circuit breaker is a switching device which can be operated manually as well as automatically for controlling and protection of
electrical power
system respectively. As the modern power system deals with huge
currents, the spacial attention should be given during designing of
circuit breaker to safe interruption of arc produced during the
operation of circuit breaker. This was the basic
definition of circuit breaker.
Introduction to Circuit Breaker
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 equipment 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. During interruption of huge current, there would
be large arcing in between switching contacts, so care should be taken
to quench these
arcs in circuit breaker in safe manner. The
circuit breaker is the special device which does all the required switching operations during
current carrying condition. This was the basic
introduction to circuit breaker.
Working Principle of Circuit Breaker
The
circuit breaker
mainly consists of fixed contacts and moving contacts. In normal "on"
condition of circuit breaker, these two contacts are physically
connected to each other due to applied mechanical pressure on the moving
contacts. There is an arrangement stored potential energy in the
operating mechanism of circuit breaker which is realized if switching signal given to the breaker. The potential energy can be stored in the
circuit breaker
by different ways like by deforming metal spring, by compressed air, or
by hydrolic pressure. But whatever the source of potential energy, it
must be released during operation. Release of potential energy makes
sliding of the moving contact at extremely fast manner. All
circuit breaker
have operating coils (tripping coils and close coil), whenever these
coils are energized by switching pulse, the plunger inside them
displaced. This operating coil plunger is typically attached to the
operating mechanism of circuit breaker,
as a result the mechanically stored potential energy in the breaker
mechanism is released in forms of kinetic energy, which makes the moving
contact to move as these moving contacts mechanically attached through a
gear lever arrangement with the operating mechanism. After a cycle of
operation of circuit breaker the total stored energy is released and hence the potential energy again stored in the operating mechanism of
circuit breaker by means of spring charging motor or air compressor or by any other means. Till now we have discussed about mechanical
working principle of circuit breaker. But there are electrical characteristics of a
circuit breaker which also should be consider in this discussion of
operation of circuit breaker.
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