The document provides an overview of circuit breakers, detailing their definitions, working principles, types, advantages, and disadvantages. It specifically discusses various types such as oil, vacuum, air blast, SF6, miniature, and earth leakage circuit breakers. The conclusion emphasizes the importance of circuit breakers in protecting electrical networks and devices from damage, highlighting the increasing use of vacuum and SF6 circuit breakers for their reliability and efficiency.

1. CIRCUIT BREAKERS
PRESENTED BY
AJAY.S
11EE02

2. Content
 Introduction to Circuit breaker
 Basic Defination Of Circuit – Breaker
 Working Principle of Circuit Breaker
 Types Of Circuit Breakers
1. Oil Circuit Breakers
2. Vacuum Circuit Breakers
3. Air Blast Circuit Breakers
4. SF6 Circuit Breakers
5. Miniature Circuit Breakers
6. Earth Leakage Circuit Breakers
 Conclusion

3. 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 equipments and the power
networks the fault current should be cleared from
the system as quickly as possible.

4. Basic Defination Of 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.
 Its basic function is to detect a
fault condition and, by interrupting
continuity, to immediately
discontinue electrical flow.

5. 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.
• 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.

6. Types Of Circuit Breakers
 Oil Circuit Breakers
 Vacuum Circuit Breakers
 Air Blast Circuit Breakers
 SF6 Circuit Breakers
 Miniature Circuit Breakers
 Earth Leakage Circuit Breakers

7. OIL CIRCUIT BREAKER
 It is designed for 11kv-765kv.
These are of two types
• BOCB (Bulk oil Circuit
Breaker)
• MOCB (Minimum oil Circuit
Breaker)
The contacts are immersed in oil
bath.
 Oil provides cooling by hydrogen
created by arc.
 It acts as a good dielectric
medium and quenches the arc.

8. Advantages:
 Oil has good dielectric strength.
 Low cost.
 Oil is easily available.
 It has wide range of breaking capability.
Disadvantages:
 Slower operation , takes about 20 cycles for arc quenching.
 It is highly inflammable , so high risk of fire.
 High maintenance cost.

9. VACCUM CIRCUIT BREAKER
 It is designed for medium voltage
range (3.3-33kv).
 This consists of vacuum of pressure
(1*10-6) inside arc extinction chamber.
 The arc burns in metal vapour when
the contacts are disconnected.
 At high voltage , it’s rate of dielectric
strength recovery is very high.
 Due to vacuum arc extinction is very
fast.
 The contacts loose metals gradually
due to formation of metal vapours.

10. Advantages:
 Free from arc and fire hazards.
 Low cost for maintenance & simpler mechanism.
 Low arcing time & high contact life.
 Silent and less vibrational operation.
 Due to vacuum contacts remain free from corrosion.
 No byproducts formed.
Disadvantages:
 High initial cost due to creation of vacuum.
 Surface of contacts are depleted due to metal vapours.
 High cost & size required for high voltage breakers.

11. AIR BLAST CIRCUIT BREAKERS
 This operates using high velocity blast of air which quenches
the arc.
 It consists of blast valve , blast tube & contacts.
 Blast valve contains air at high pressure.
 Blast tube carries the air at high pressure & opens the moving
contact attached to spring.
 There is no carbonization of surface as in VCB.
 Air should be kept clean & dry to operate it properly.

13. Advantages:
 High speed operation as compared to OCB.
 Ability to withstand frequent switching.
 Facility for high speed reclosure.
 Less maintenance as compared to OCB.
Disadvantages:
 Little moisture content prolongs arcing time.
 Pressure should be checked frequently for frequent
operation.
 Risk of fire hazards due to over voltages.
 It can’t be used for high voltage operation due to prolonged
arc quenching.

14. SF6 CIRCUIT BREAKERS
 It contains an arc interruption chamber containing SF6 gas.
 In closed position the contacts remain surrounded by SF6 gas
at a pressure of 2.8 kg/cm2 .
 During opening high pressure SF6 gas at 14 kg/cm2 from its
reservoir flows towards the chamber by valve mechanism.
 SF6 rapidly absorbs the free electrons in the arc path to form
immobile negative ions to build up high dielectric strength.
 It also cools the arc and extinguishes it.
 After operation the valve is closed by the action of a set of
springs.
 Absorbent materials are used to absorb the byproducts and
moisture.

16. Advantages:
 Very short arcing period due to superior arc quenching
property of SF6 .
 Can interrupt much larger currents as compared to other
breakers.
 No risk of fire.
 Low maintenance, light foundation.
 No over voltage problem.
 There are no carbon deposits.
Disadvantages:
 SF6 breakers are costly due to high cost of SF6.
 SF6 gas has to be reconditioned after every operation of the
breaker, additional equipment is required for this purpose.

17. MINIATURE CIRCUIT BREAKER
 An MCB is an Electromagnetic Device which Operates and
Disconnects the Circuit when the Current reaches a pre
determined value.
 It is most modern substitute for conventional rewireable fuse
with most accurate & efficient system in over-load & short
circuit protection. In fact, it provides over-load protection &
short circuits protection whereas FUSE offers short circuit
protection only.
 An MCB will normally operate at 1.25 times it rated current i.e.
20 A. MCB operates at 25 A compared with 30 A for cartridge
fuse or 40 A for rewireable type of fuse of the same rating.

18.  Also the MCB which has tripped due to over-load or short
circuit can be readily identified as the dolly or toggle or
operating knob automatically moves to the “OFF” position.
PRINCIPLE OF OPERATION :
 MCB is a device which operates on the two metallic plates for
the protection against over-load & short circuit.
 1. Thermal for normal overload protection.
 2. Magnetic for the short Circuit protection .

19.  The thermal operation is achieved by metallic strip, which
defects when heated by any over current flowing through
it .
 In doing so release the latch mechanism and causes the
contacts to open.
 When short Circuit occurs, the rising energizes the
solenoid operating plunger to strike the trip lever causing
immediate release of the latch mechanism

20. CLASSIFICATION OF MCB’s:
1. L-Series MCB for Lighting Circuits:-
Suitable for resistive Load installation with Low
& Steady Currents like heaters , ovens, geysers, electric
irons , etc. The L-Series MCB’s are also used for
protection of distribution equipment like wires, Cables,
metering equipment etc.
2.G-Series MCB for Motor Circuits:-
It is suitable for use in installation with high
inrush current peaks which require closer over-load
protection. These include inductive Loads such as motors,
A.C. transformers , halogen –fluoresent –sodium vapour
lamps,machine tools etc.

21. APPLICATION OF MCB:
 They are required in homes, offices, shops distribution boards
for protection of individual circuit & complete wiring system
in that buildings through main circuits.
 Whatever be the application, these MCB’s
offer perfect over-load & circuit protection.
ON
OFF

22. EARTH LEAKAGE CIRCUIT
BREAKER :
 An Earth Leakage Circuit Breaker is a safety device used in
electrical installations with high earth impedance to prevent
Shock.
 Many electrical installations have a relatively high earth
impedance.
These may be due to use of local earth rod to dry ground
conditions.
 These installations have a major problem if no ELCB is used.
During live to earth fault current,two conditions occur. Because
earth impedance is high,

23. 1. Not enough current exist to trip a fuse or circuit breaker, so
condition persists uncleared indefinitely .
2. The high impedance earth can not keep the voltage of all exposed
CPC connected metalwork to safe voltage all such metalwork
may rise to close to live conductor voltage.
TYPES OF ELCB:
I. Voltage Operated:-
They Provide a major advance in safety for mains electrical
supplies with inadequate earth impedance.
II. Current Operated:-
They Provide protection against earth leakage, through the
details & method of operation are different.

24. PRINCIPLE OF OPERATION:
 It is a current operated device designed to operate when a
leakage current exceeds a pre-determined value. It essentially
consist of an operating coil & a trip mechanism which operates
contacts controlling the supply to the circuit concerned.
 Consider a single-phase circuit. The two supply wires i .e. phase &
neutral are fed through separate winding of current transformer as
shown in the fig: another
winding controls the tripping
mechanism.

25. Ip = In
Therefore, the fluxes linking the phase & neutral conductors
are equal in magnitude & opposite in direction. Thus, no fluxes
links with tripping. Winding.
ADVANTAGES :
 They are less sensitive to fault conditions , therefore have
less nuisance strips.
 They can be arranged to protect against
cable damage only.
 And not strip on faults in down line
installations.

26. DISADVANTAGES:
 They do not detect faults that don’t pass current through the
CPC to the earth rod.
 They do not allow a single building system to be easily spilt
into multiple sections with independent fault protection,
because earthing system are usually bounded to pipe work.
 ELCBs introduce additional resistance & an additional point of
failure into earthing systems.

27. CONCLUSION:
Therefore, we conclude that circuit breaker is the most essential
part of the electrical networks as it protects every device from
damage. It helps us to detect the fault and area affected by it.
Nowadays vacuum and SF6 circuit breakers are widely used due
to their reliable and fast operations.