This document discusses circuit breakers, including their purpose, types, and working principles. It begins by defining a circuit breaker as a switching device that can manually and automatically control and protect an electrical power system by interrupting faults. It then describes the main types of circuit breakers used in low, medium, and high voltage applications. Specific types like MCBs, MCCBs, RCCBs, and ELCBs are also defined and their differences explained. The document concludes by summarizing the critical role of circuit breakers in protecting electrical networks and devices.

1. ELECTRICAL SYSTEM
Chiranjit Halder (EE-2nd Year-45)

2. ELECTRICAL CIRCUIT
BREAKER
Operation and Types of Circuit Breaker

3. Contents:
1. What is Circuit Breaker?
2. Introduction to Circuit Breaker
3. Need of Circuit Breaker
4. Types of Circuit Breaker
5. MCB (Miniature Circuit Breaker)
6. MCCB (Molded Case Circuit Breaker)
7. Difference between MCB and MCCB
8. RCCB (Residual Current Circuit Breaker)
9. ELCB (Earth Leakage Circuit Breaker)
10. Difference between RCCB and ELCB
11. Working Principle of Circuit Breaker (with an animation)
12. Conclusion

4. What is Circuit Breaker?
◦ An Electrical Circuit Breaker is a switching device which can be operated
manually and automatically for controlling and protecting an Electrical Power
System.
◦ As the modern power system deals with huge currents, special attention
should be given during designing of a circuit breaker to ensure it is able to
safely interrupt the arc produced during the closing of a circuit breaker.
◦ Primarily the circuit breakers are used for switching of different kinds of load
in Industries, Buildings, Commercial Complexes, and Hotels, etc.

5. INTRODUCTION
To Circuit Breaker

6. The modern power system deals with huge power network and huge
numbers of associated electrical equipment. During a short circuit
fault or any other type of electrical fault (such as electric cable faults),
a high fault current will flow through this equipment as well as the
power network itself. This high current may damage the equipment
and networks permanently.

7. For saving these pieces of equipment and the power networks, the fault current
should be cleared from the system as quickly as possible. Again after the fault is
removed, 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 the power system, different switching operations are
required to be performed.

8. 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 the interruption of large current, there would be large arcing in between
switching contacts, so care should be taken to quench these arcs in circuit breaker
in a 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.

9. Need of Circuit Breaker
Many kind of abnormal conditions are there which exist in our electrical system that have the
potential to damage the circuit & its components. These conditions are defined as ‘FAULTS’.
Further, fault is categorized as mentioned below:
• Overload
• Short Circuit
• Earth
In order to keep our electrical components & system safe, it is mandatory to protect our system
against the above faults. This leads to the need of circuit breaker.

10. Types of Circuit Breaker
Circuit breakers mainly are categorized on the basis of application as per voltage:
1) Low Voltage Circuit Breaker
• MCCB
• ACB
• MCB
• RCCB
2) Medium Voltage Circuit Breakers
3) SF6/VACUUM Circuit Breakers
4) High Voltage Circuit Breakers
• VCB
• SF6
• OCB
• ABCB

11. MCB (Miniature Circuit Breaker)
MCB automatically switches OFF electrical circuit during
any abnormal condition in the electrical network such as
overload & short circuit conditions. However, fuse may
sense these conditions but it has to be replaced though
MCB can be reset. The MCB is an electromechanical device
which guards the electric wires &electrical load from
overcurrent so as to avoid any kind of fire or electrical
hazards. Handling MCB is quite safer and it quickly
restores the supply. When it comes to house
applications, MCB is the most preferred choice for
overload and short circuit protection. MCB can be reset
very fast & don’t have any maintenance cost. MCB works
on bi-metal respective principle which provides protection
against overload current & solenoid short circuit current.

12. MCCB (Molded Case Circuit Breaker)
MCCB is another type of electrical protection device
which is used when load current exceeds the limit of
a miniature circuit breaker. The MCCB provides
protection against overload, short circuit faults and
is also used for switching the circuits. It can be used
for higher current rating and fault level even in
domestic applications. The wide current ratings and
high breaking capacity in MCCB find their use in
industrial applications. MCCB can be used for
protection of capacitor bank, generator protection
and main electric feeder distribution. It offers
adequate protection whenever an application
requires discrimination, adjustable overload setting
or earth fault protection.

13. Difference between MCB and MCCB
MCB
◦ It stands for Miniature Circuit Breaker.
◦ Rated current not more than 125 Ampere.
◦ Its interrupting current rating is under
10KA.
◦ Judging from their power capacities, MCB
is mainly used for low Breaking capacity
requirement mainly domestic.
◦ Its trip characteristics are normally not
adjustable since they basically cater to low
circuits.
MCCB
◦ It stands for Molded Case Circuit Breaker.
◦ Rated Current up to 1600A.
◦ Their interrupting current ranges from around
10KA-85KA.
◦ MCCB is mainly used for both low and high
Breaking capacity requirements mainly
industrial.
◦ Its trip current may be fixed as well as
adjustable for overload and magnetic setting.

14. RCCB (Residual Current Circuit
Breaker)
This residual current device is basically an electrical wiring
device that disconnects the circuit whenever there is leakage
of current flow through the Human body or the current is
not balanced between the phase conductor. It is the safest
device to detect and trip against electrical leakage currents,
thus ensure protection against electric shock caused by
direct contacts. RCCB is generally used in series with an
MCB which protects them from over current and short
circuit current. Both phase and neutral wires are connected
through a RCCB device. These are an extremely effective
form of shock protection & widely used for protection from
a leakage current of 30,100 & 300mA. It is essential
lifesaving equipment used to protect the human body from
electrical and is mandatory in many states for domestic
installation.

15. ELCB (Earth Leakage Circuit Breaker)
ELCBs have the same function
as RCCB but are voltage sensor
device. However, this is an old
technology & is not in common
use. RCCB being a current
sensitive device, have a better
advantage over ELCB.

16. Difference between RCCB and ELCB
RCCB
◦ RCCB refers to ear stands for Residual
Current Circuit Breaker.
◦ It is a new name and refers to current
operated devices.
◦ It ensures 100% detection of leakage
current& is available to sense the AC as well
as DC leakage current.
◦ RCCB has no connection with the earth wire
and that’s why it can trip when both currents
(phase and neutral) are different and it
withstands up to both the currents are same.
ELCB
◦ ELCB stands for Electric Leakage Circuit
Breaker.
◦ ELCB refers to voltage operated earth
leakage device.
◦ It is not preferable as it can only detect
current that flow back through the main
earth wire.
◦ ELCB is working based on Earth leakage
current. These devices measured the voltage
on the earth conductor; if this voltage was
not zero this indicated a current leakage to
earth.

17. WORKING PRINCIPLE OF
CIRCUIT BREAKER
(With an animation)

18. The circuit breaker has to carry large rated or
fault power. Due to this large power, there is
always dangerously high arcing between
moving contacts and fixed contact during
operation of the circuit breaker. Again as we
discussed earlier the arc in circuit breaker can be
quenching safely if the dielectric strength
between the current carrying contacts of circuit
breaker increases rapidly during every currentt
zero crossing of the alternating current.
The dielectric strength of the media in between
contacts can be increased in numbers of ways,
like by compressing the ionized arcing media
since compressing accelerates the deionization
process of the media, by cooling the arcing
media since cooling increase the resistance of
arcing path or by replacing the ionized arcing
media with fresh gasses. Hence some arc
quenching processes should be involved in the
operation of the circuit breaker.
Although circuit breakers perform their function
independently and without supervision, there
are also remote control circuit breakers which
can be operated on demand at a distance.

19. 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.