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

Project AdvisorProject Advisor::

ENGR. JAHANGIR AKHTAR KHANENGR. JAHANGIR AKHTAR KHAN

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

Methods of Arc Extinction

High Resistance Method

Low Resistance Method

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

Air cushion

Bulk Oil Circuit Bulk Oil Circuit breakerbreaker

Low Oil Circuit BreakerLow Oil Circuit Breaker

► Consists of two Consists of two parts.parts.

►Supporting Supporting Chamber.Chamber.

►Circuit-Breaking Circuit-Breaking chamber( consist chamber( consist of fixed and of fixed and moving contactmoving contact) )

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 Oil has to be replaced after some

operations because of the carbonization of operations because of the carbonization of oil.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.

Vacuum Circuit BreakerVacuum Circuit Breaker

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 & SF6 gas is non flammable, non toxic &

chemical inert gas.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 Ability to interrupt low and high fault

current.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

THE ENDTHE END