2CONTENTS Introduction History Basic Element Of circuit breaker Type Of Circuit BreakersAdvantagesConclusionReferences
3INTRODUCTIONCircuit 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.
4HISTORYInspired 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.
5BASIC ELEMENT OF CIRCUIT BREAKER:- 1.Contact.Mechanism.3.Operating4.Arc quenches medium.2.Insulation.
6TYPES OF CIRCUIT BREAKER:- Low voltage air circuit breaker.Oil circuit breaker.Air blast circuit breaker.SF6 circuit breaker.Vacuum circuit breaker.
7Low 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 categoryMCCB (Molded Case Circuit Breaker)—rated current up to 2500 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.
8Bulk 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 breaker115KV BULK OIL CIRCUIT BREAKERMinimum Oil Circuit Breaker(MOCB)Contains less amount of oil.The design concept still there.33kv MINIMUM Oil Circuit Breaker
9AIR BLAST CIRCUIT BREAKER(ABCB) Some advantages over OCB:-High speed operationAbility to withstand frequent switchingFacility for high speed re-closureComparatively less maintenanceUSES:-Used for special application like for the high power laboratories world wide.
10VACUUM 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 operateThey have silent operation.The dielectric recovery rate is faster.
11SF6 CIRCUIT BREAKERSSF6 CIRCUIT BREAKER400 kV SF6 live tank circuit breakersSome of the outstanding properties of SF6 gas are:Electrical& thermal properties:High dielectric strengthOutstanding arc-quenching abilityExcellent thermal stabilityGood thermal conductivityPhysical & chemical attributes:Chemically inertNon toxicNon-inflammableNon-corrosiveAdvantages of SF6:Increased safetyReduction in size & Simplified designReduction in weight & Reliability of operation & noiseless operationEasy for installation & maintenance
12ADVANTAGES Circuit breakers have many good design points; such as Double Fault ProtectionManually switchable modeBuilt in safety features to prevent spark ignition & meltdown.Very much effective & compact in nature.
13ConclusionProper maintenance can be performed and power systems kept in a safe, reliable condition with the proper mixture of:Common senseTrainingManufacturer’s literature and spare parts.Circuit breakers, if installed within their ratings and properly maintained, shouldOperate 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.