Circuit breaker


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A power point description on circuit breakers

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Circuit breaker

  1. 1. A presentation on Circuit Breaker By Priyankar Misra EEE VITAM
  2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 18. Disadvantages of circuit breakers • Initial cost is high • Reacts less quicker than a fuse • More sensitive to vibration and movement
  19. 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