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CCIRCUIT IRCUIT BBREAKERREAKERpresented by: presented by: M Aamir sohail M Aamir sohail
khankhan & &
sufyan saleem sufyan saleem
Dept, of electrical Dept, of electrical engineering bahaudain engineering bahaudain
zakariya university Multan , zakariya university Multan , PakistanPakistan
WHAT IS A CIRCUIT BREAKER?WHAT IS A CIRCUIT BREAKER?
►A circuit breaker is an equipment that A circuit breaker is an equipment that breaks a circuit either manually or breaks a circuit either manually or automatically under all conditions at automatically under all conditions at no load, full load or short circuit.no load, full load or short circuit.
Operating PrincipleTwo contacts called electrode remains closed under normal operating conditions. When fault occurs on any part of the system, the trip coil of the circuit breaker get energized and contacts are separated.
Arc PhenomenonAn arc is struck when contacts are separated. The current is thus able to continue. Thus the main duty of a circuit breaker is to distinguish the arc within the shortest possible time.
The arc provides the low resistance path to the current and the current in the circuit remains uninterrupted.
The arc resistance depends upon the following factors.
Degree of ionizationLength of the arcCross Section of the arc
TYPES OF
CIRCUIT BREAKER
OIL CIRCUIT BREAKER
AIR BLAST CIRCUIT BREAKER
SF6 CIRCUIT BREAKER
VACCUMCIRCUIT BREAKER
Breaker Used In 132KV Breaker Used In 132KV Grid StationGrid Station
►Oil Circuit BreakerOil Circuit Breaker►Vacuum Circuit breakerVacuum Circuit breaker►SF6 Circuit BreakerSF6 Circuit Breaker
Low Oil Circuit BreakerLow Oil Circuit Breaker
► Consists of two parts.Consists of two parts.►Supporting Chamber.Supporting Chamber.►Circuit-Breaking Circuit-Breaking
chamber( consist of chamber( consist of fixed and moving fixed and moving contactcontact) )
Disadvantages Of Oil Circuit Disadvantages Of Oil Circuit BreakerBreaker
► It is inflammable and there is a risk of fire. It is inflammable and there is a risk of fire. ► It may form an explosive mixture with air.It may form an explosive mixture with air.► It requires maintenance.It requires maintenance.►Absorbs moisture, so dielectric strength Absorbs moisture, so dielectric strength
reduces.reduces.►Oil leakage problem.Oil leakage problem.►Oil has to be replaced after some operations Oil has to be replaced after some operations
because of the carbonization of oil.because of the carbonization of oil.
Vacuum Circuit BreakerVacuum Circuit Breaker
►Vacuum is used as an arc quenching Vacuum is used as an arc quenching medium.medium.
►Have greatest insulating strength.Have greatest insulating strength.►1010-7-7 to 10 to 10-5-5 pressure is to be pressure is to be
maintained.maintained.►Used in 11KV panel in control room of Used in 11KV panel in control room of
grid station.grid station.
AdvantagesAdvantages
►Compact, reliable and have longer life.Compact, reliable and have longer life.►No fire hazards.No fire hazards.►No generation of gas during and after No generation of gas during and after
operation.operation.►Can interrupt any fault current.Can interrupt any fault current.►No noise is produced while operating.No noise is produced while operating.►Require less power for control Require less power for control
operation. operation.
SF6 Circuit BreakerSF6 Circuit Breaker
1.1. Sulphur Hexafluoride (SF6) gas is used as an Sulphur Hexafluoride (SF6) gas is used as an arc quenching medium.arc quenching medium.
2.2. SF6 is an electro-negative gas.SF6 is an electro-negative gas.3.3. It has strong tendency to absorb electrons.It has strong tendency to absorb electrons.4.4. When contact are opened in a high pressure When contact are opened in a high pressure
flow of SF6 gas, arc produced.flow of SF6 gas, arc produced.5.5. Free electron in the arc are captured by the Free electron in the arc are captured by the
gas.gas.6.6. Which build up enough insulation strength to Which build up enough insulation strength to
extinguish arc.extinguish arc.7.7. it is much effective for high power and high it is much effective for high power and high
voltages services,voltages services,
Advantages Advantages
►Simple construction, less cost.Simple construction, less cost.
►SF6 gas is non flammable, non toxic & chemical inert gas.SF6 gas is non flammable, non toxic & chemical inert gas.
►Same gas is recirculated in the circuit.Same gas is recirculated in the circuit.
►Maintenance free C.B.Maintenance free C.B.
►Ability to interrupt low and high fault current.Ability to interrupt low and high fault current.
►Excellent Arc extinction.Excellent Arc extinction.
Advantages Of SF6 Over Oil Circuit Advantages Of SF6 Over Oil Circuit BreakersBreakers
► Short arcing timeShort arcing time► Can interrupt much larger currentsCan interrupt much larger currents► Gives noiseless operation due to its closed Gives noiseless operation due to its closed
gas circuitgas circuit► No moisture problemNo moisture problem► No risk of fireNo risk of fire► No carbon deposits. So no tracking and No carbon deposits. So no tracking and
insulation problemsinsulation problems► Low maintenance costLow maintenance cost
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