A power point description on circuit breakers

1. A presentation on Circuit Breaker
By
Priyankar Misra
EEE
VITAM

2. Introduction
• Automatically operated electrical switch,
protect an electrical switch from overload or
short circuit
• Basic function-fault detection and interrupt
current flow
• Can be reset to resume application
• Available in a variety of size

3. Origin
• Early form, developed by Thomas Edison in
1879 patent application-to protect lighting
circuit wiring from accidental short circuit
• Modern miniature circuit breaker ,patented by
Brown, Boveri and Cie in 1924.

4. Operation
• A fault condition must be detected
• Once fault detected, contacts within circuit
breaker, some mechanical stored energy
stored in the circuit breaker and some energy
utilized from the fault current.
• Circuit breaker contacts carry the load current
without getting heated
• Arc in generated, which is controlled and
extinguished in a controlled way

5. Arc interruption
• Low voltage MCB-air, larger ratings –metallic
or non metallic arc clutches
• Gas circuit breakers-dielectric strength of
sulphur hexafluoride
• Vacuum circuit breakers-minimal arching
• Air circuit breakers-compressed air

6. Short circuit current
• Circuit breakers-rated-normal current they can
carry and maximum short circuit current they
can safely carry
• Under short circuit conditions-current much
larger then normal currents flow-electrical
contacts open to interrupt large current arc is
produced

7. Types of circuit breakers
• Low voltage circuit breakers
• Magnetic circuit breakers
• Thermal magnetic circuit breakers
• Common trip breakers
• Medium voltage circuit breakers
• Sulfur hexafluoride high voltage circuit breakers
• Disconnecting circuit breakers
• Carbon dioxide high voltage circuit breakers

8. Low voltage circuit breakers
• Common in domestic,
industrial and commercial
applications-include
MCB(type B, type C and
type D) and MCCB.
• Characteristics –given by
international standards-
often installed in draw
out enclosures-also made
for DC applications

9. Magnetic circuit breakers
• Magnetic circuit breakers-
solenoid-pulling action
increases the current
• when current increases
beyond rated-solenoid’s pull
releases the latch-contacts
open by spring action
• Some magnetic circuit
breakers-incorporate a
hydraulic time delay-during
overload fluid restricts
solenoid motion-permitting
short current surges

10. Thermal magnetic circuit breakers
• Mostly found in
distribution boards-use
both techniques –
electromagnet
responding
instantaneously to large
surges in current,
bimetallic strip
responding to less
extreme but longer term
over current conditions

11. Common Trip breakers
• Supplying a branch circuit-
more than one live
conductors-when one pole
trips all live conductors must
be interrupted.
• Either contain two or three
tripping mechanism-two pole
common trip breakers are
common on 120/240 volt
system, three pole common
trip breakers are used to
supply three phase electric
supply to large machines
• Two or four pole breakers may
be used-to disconnect multiple
phase ac or neutral wire

12. Medium voltage circuit breakers
• Rated between 1-72 KV,
operated by current
sensing protective relays
operated through current
transformer.
• Classified according to the
medium used to
extinguish the arc-
vacuum circuit breakers,
air circuit breakers and
sculpture hexafluoride
circuit breakers

13. High voltage circuit breakers
• Protect and control electrical
power transmission-usually
72.5 KV or higher-mostly
solenoid operated with
current sensing relays
operated through current
transformers
• Broadly classified according to
the medium used to
extinguish the arc-bilk oil,
minimum oil, air blast,
vacuum, sulphur
hexafluoride, carbon dioxide

14. Sulphur hexafluoride high voltage
circuit breakers
• Uses contacts surrounded
by sulphur hexafluoride
to quench the arc, often
used for transmission
level voltages and may be
incorporated into
compact gas-insulated
switchgear
• In cold climate
supplemental heating or
de rating of the circuit
breakers may be required

15. Disconnecting circuit breakers
• High voltage circuit
breaker, modeled after
sulphur hexafluoride
circuit breaker
• Disconnecting function
integrated in the breaking
chamber, increases the
availability, reduces the
space requirement within
the substation, increases
the reliability.

16. Carbon dioxide high voltage circuit
breakers
• Works on the same
principle as sulphur
hexafluoride circuit
breaker, can also be
produced as a
disconnecting circuit
breakers, high voltage
breaker
• Possible to reduce nearly
10 tons of carbon dioxide
emissions during the
product’s life time

17. Advantages of circuit breaker
• Disconnect the entire load instead of a single
load
• Provide better protection to 3 phase motors
• Less cost
• Provides greater reliability and safety
• Cost of ownership

18. Disadvantages of circuit breakers
• Initial cost is high
• Reacts less quicker than a fuse
• More sensitive to vibration and movement

19. Conclusion
• Circuit breaker is an essential part of electrical
network as it protects every device from
electrical damage
• Helps us to detect the fault and the area
associated with it
• Nowadays vacuum and sulphur hexaflouride
circuit breakers are widely used due to their
reliable and fast operations