CIRCUIT BREAKERS

CONTENTS Introduction History Basic Element Of circuit breaker Type Of Circuit Breakers Advantages Conclusion References

INTRODUCTION Circuit breakers are the sentinels of a power system. They are required to switch circuit 'ON', both under normal and abnormal conditions . 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.

HISTORY Inspired by the works of American scientist Joseph Henry and English scientist Michael Faraday, the circuit breaker was invented in 1836 by an American, Charles Grafton. An early form of circuit breaker was described by Thomas Alva Edison in an 1879 patent application, although his commercial power distribution system used fuses. Its purpose was to protect lighting circuit wiring from accidental short-circuits and overloads. A modern miniature circuit breaker similar to the ones now in use was patented by Brown, Boveri&Cie in 1924.

BASIC ELEMENT OF CIRCUIT BREAKER:- 1.Contact. Mechanism. 3.Operating 4.Arc quenches medium. 2.Insulation.

TYPES OF CIRCUIT BREAKER:- Low voltage air circuit breaker. Oil circuit breaker. Air blast circuit breaker. SF6 circuit breaker. Vacuum circuit breaker.

Low voltage circuit breakers MCB (Miniature Circuit Breaker)—rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category MCCB (Molded Case Circuit Breaker)—rated current up to 2500 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.

Bulk Oil Circuit Breaker(BOCB) Minimum Oil Circuit Breaker(MOCB) Contains more oil. Due the development of arc control devices BOCB design is progressively reduced. 115 kV bulk oil circuit breaker 115KV BULK OIL CIRCUIT BREAKER Minimum Oil Circuit Breaker(MOCB) Contains less amount of oil. The design concept still there. 33kv MINIMUM Oil Circuit Breaker

AIR BLAST CIRCUIT BREAKER(ABCB) Some advantages over OCB:- High speed operation Ability to withstand frequent switching Facility for high speed re-closure Comparatively less maintenance USES:- Used for special application like for the high power laboratories world wide.

VACUUM CIRCUIT BREAKER It can be used up to 132KV;But widely used for 11KV & 33KV. VCB are generally very expensive due to its materials processing & technique. ADVANTAGES:- Maintenance free & non flammable in nature. Requires relatively less mechanical energy to operate They have silent operation. The dielectric recovery rate is faster.

SF6 CIRCUIT BREAKERS SF6 CIRCUIT BREAKER 400 kV SF6 live tank circuit breakers Some of the outstanding properties of SF6 gas are: Electrical& thermal properties: High dielectric strength Outstanding arc-quenching ability Excellent thermal stability Good thermal conductivity Physical & chemical attributes: Chemically inert Non toxic Non-inflammable Non-corrosive Advantages of SF6: Increased safety Reduction in size & Simplified design Reduction in weight & Reliability of operation & noiseless operation Easy for installation & maintenance

ADVANTAGES Circuit breakers have many good design points; such as Double Fault Protection Manually switchable mode Built in safety features to prevent spark ignition & meltdown. Very much effective & compact in nature.

Conclusion Proper maintenance can be performed and power systems kept in a safe, reliable condition with the proper mixture of: Common sense Training Manufacturer’s literature and spare parts. Circuit breakers, if installed within their ratings and properly maintained, should Operate trouble-free for many years. If operated outside of their rating or without proper maintenance. May cause serious injury or even death of employee working in the area. Care should be taken when applying beaker failure to ring bus and breaker and one half.

REFERANCE http://www.google.co.in/en/circuit_breaker.html   http://www.google.co.in/en/circuit_breaker.html http://en.wikipedia.org/wiki/circuit_breaker http://www.ieee.co.in/info/circuitbreaker_notes.docx http://www.googlebooks/ebooks.com/ http://www.freeessays.cc/db/17/etn6.shtml http://www.element14.com/community/groups/circuit-protection http://www.jyotibooksdepot.com http://www.newagepublishers.com http://www.optc.org

THANK YOU