SEMINAR ON

CIRCUIT BREAKERS

What Is Circuit Breaker?What Is Circuit Breaker?

Working Principle Of Circuit Breaker

Working Principle Of Circuit Breaker

Arc PhenomenonArc Phenomenon

1. Degree of ionization

2. Length of the arc

3. Cross-section of the arc

High Resistance Method

1. Lengthening the arc

2. Cooling the arc

3. Reducing cross section of

arc

4. Splitting the arc

Low Resistance Method

1.Lengthening of the gap

2. High pressure

3.Cooling

4.Blast effect

Methods Of Arc ExtinctionMethods Of Arc Extinction

Terms Related To Circuit BreakersTerms Related To Circuit Breakers Arc Voltage

Restriking Voltage

Recovery Voltage

Different Types Of Circuit BreakerDifferent Types Of Circuit Breaker Oil Circuit Breaker

Air Blast Circuit Breaker

Sulpher Hexafluroide Circuit Breakers

Vacuum Circuit Breakers

Low Voltage Circuit Breakers

Oil Circuit BreakerOil Circuit Breaker

• These are the oldest type circuit breakers.

• The separating contacts are made to separate within an insulating oil, which has better insulating properties than air.

• Oil circuit breakers have virtues of reliability, simplicity and relative cheapness.

• By connecting several interrupting mechanism in series, the voltage rating of the breaker can be increased.

• By careful design the interrupting capacity rating can be increased up to 26000 MVA.

• Quiet operation.

Advantages-

Disadvantages-

• The breaker contains flammable oil , consequently it should located outdoor.

• Oil breakdown at high temperature forms carbon which gets dissolved in the oil, this increases the oil conductivity.

• Becomes an environmental hazard if spillage occurs.

Air –Blast Circuit BreakerAir –Blast Circuit Breaker

• These breakers employ a high pressure air blast as an arc quenching medium.

• The contacts are opened in a flow of air blast.

• The air blast cools the arc and sweeps away the arcing products to the atmosphere.

• This rapidly increases the dielectric strength of the medium between contacts and prevents from arc.

• The arc is extinguished and flow of current is interrupted.

Principle Of Operation

(i) Axial-blast type (ii)Cross-blast type (iii)Radial-blast type

Types

• The risk of fire is eliminated.• The arcing products are completely removed by the blast. • The arcing time is very small due to the rapid build up of

dielectric strength between contacts.

Advantages-

Disadvantages-• Air has relatively inferior arc extinguishing properties.• Air blast circuit breakers are very sensitive to the variations in the

rate of restriking voltage. • Considerable maintenance is required for the compressor plant

which supplies the air blast.

Application-

The air blast circuit breakers are finding wide applications in high voltage installations. Majority of the circuit breakers for voltages beyond 110 kV are of this type.

Principle of Operation

Working

Advantage & Disadvantage

Application

Vacuum Circuit BreakersVacuum Circuit Breakers

SF6 Circuit BreakerSF6 Circuit Breaker

• Properties Of Sulphur Hexafluoride Gas

• Extremely Stable

• Moisture Content Harmful

• Thermal Conductivity Higher

• Chemical Stable Upto 500 Degree Centigrade

• Higher Dielectric Strength

• Colourless, odourless

Principle Of OperationPrinciple Of Operation

• Very short arcing time• Non-inflammable• High dielectric strength 2 to 3 time that of air• Noiseless operation• Minimum maintenance

Advantages-

Disadvantages-

• Sealing Problems• Poisonous• Special Facility Required

Application-

• Capable of dealing current up to 60 kA and voltages ranges in the range up to 50-80KV.

• Also developed for voltages 115kV to 230 kV , power ratings 10 MVA to 20 MVA.

The purpose of this seminar was the study of circuit breaker, and we know circuit breaker plays a vital role in power system. By this seminar we gather new information about circuit breaker as well as power system, which will help us in other in the journey of electrical engineering.

CONCLUSIONCONCLUSION

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