SEMINAR REPORT

ON

BRANCH-EEE.

CONTENTSCONTENTS

• IntroductionIntroduction

• Operating Principle of Circuit BreakerOperating Principle of Circuit Breaker

• Over view of SF6(Electrical properties)Over view of SF6(Electrical properties)

• Physical and chemical propertiesPhysical and chemical properties

• AdvantageAdvantage

• Principle of operation of SF6 CBPrinciple of operation of SF6 CB

• ConclusionConclusion

• ReferencesReferences

WHAT IS A CIRCUIT WHAT IS A CIRCUIT BREAKER?BREAKER?

A circuit breaker is an equipment A circuit breaker is an equipment which canwhich can

make or break a circuit either make or break a circuit either manually or automatically under manually or automatically under normal conditionsnormal conditions

break a circuit automatically under break a circuit automatically under abnormal conditionsabnormal conditions

Fixed contact

Moving contact

ARC

Fixed contact

Moving contact

ARCARC IS QUENCHED BY MEDIUM

IN A CIRCUIT BREAKER

OPERATING PRINCIPLE OF BREAKER

OVERVIEW OF ARCS IN OVERVIEW OF ARCS IN BREAKERS-:BREAKERS-:

During the separation During the separation of contacts, due to of contacts, due to large fault current large fault current and high current and high current density at the density at the contact region the contact region the surrounding medium surrounding medium ionises and thus a ionises and thus a conducting medium conducting medium is formed. This is is formed. This is called the called the ARC.ARC.

PRODUCTION OF ARC PRODUCTION OF ARC

Factors responsible for arc:-Factors responsible for arc:-

Potential difference between the Potential difference between the contactscontacts

Ionized particles between the contactsIonized particles between the contacts

By removing any one of these the arc By removing any one of these the arc can be quenched.can be quenched.

OVERVIEW OF SFOVERVIEW OF SF66 GAS:-GAS:-

1. High dielectric strength 1. High dielectric strength

2. Excellent arc quenching ability 2. Excellent arc quenching ability

3. Excellent thermal stability 3. Excellent thermal stability

4. Good thermal conductivity 4. Good thermal conductivity

Electrical properties

1. Chemically inert 1. Chemically inert

2. Non-toxic2. Non-toxic

3. Non-corrosive 3. Non-corrosive

4. Non-flammable 4. Non-flammable

Physical & Chemical properties

5. High density 5. High density

Dielectric properties of SFDielectric properties of SF66 gas:-gas:-

DS of SFDS of SF66 is 2.5 times of is 2.5 times of airair

DS of SFDS of SF66 is 30% less is 30% less than oilthan oil

DS of SFDS of SF66 is equal to oil is equal to oil at 650 gm/cm2at 650 gm/cm2

And 15% higher at 1.25 And 15% higher at 1.25 Kg/cm2Kg/cm2

Advantages of SFAdvantages of SF66 gas:- gas:-

1. Increased safety 1. Increased safety

2. Reduced size 2. Reduced size

3. Easy installation 3. Easy installation

4. Low maintenance 4. Low maintenance

SFSF66 CIRCUIT CIRCUIT BREAKERBREAKER

OPERATIONOPERATION

SFSF66 DECOMPOSITION DECOMPOSITION PRODUCTSPRODUCTS

SF6

SF4 + 2F

SOF2 +

2HF

MFn

SO2 + HF

SiF4 + 2 H2O

SPARK

H2O

H2O

SiO2

M

magnitude & duration of discharge

materials of construction of equipment

contamination levels of moisture and air inside the equipment

Amount of each decomposition product depends on :-

REMOVAL OF SFREMOVAL OF SF66 BYPRODUCTS:-BYPRODUCTS:-Byproducts are corrosive & likely to affect the Byproducts are corrosive & likely to affect the

organic materials.organic materials.Absorbent materials used in circuit breakersAbsorbent materials used in circuit breakers activated alumina( effective for activated alumina( effective for SOF2,H2S,SF2)SOF2,H2S,SF2) molecular sievesmolecular sieves( sodalime-( sodalime-CaO.NaOH)-CaO.NaOH)-

removes stable gases such asremoves stable gases such as SF4,SiF4 & S2F2 SF4,SiF4 & S2F2

So suggested mix is 50/50 of sodalime& So suggested mix is 50/50 of sodalime&

alumina. The suggested weight of alumina. The suggested weight of absorbent is 10% of the weight of the gasabsorbent is 10% of the weight of the gas

ADVANTAGES OF SFADVANTAGES OF SF66 CIRCUIT BREAKERSCIRCUIT BREAKERS

Very short arcing periodVery short arcing period Can interrupt much Can interrupt much

larger currents as larger currents as compared to other compared to other breakersbreakers

No risk of fireNo risk of fire Low maintenance, light Low maintenance, light

foundation, minimum foundation, minimum auxiliary equipmentsauxiliary equipments

No over voltage problemNo over voltage problem

CONCLUSIONCONCLUSION

Harnessing the utilities of Harnessing the utilities of SFSF66 gas gas in power system and power in power system and power system equipments, makes it system equipments, makes it more reliable and safer to use.more reliable and safer to use.

The countless advantages this The countless advantages this SFSF66 gas has to offer will take us to gas has to offer will take us to new heights in the prevalent new heights in the prevalent orthodox power system.orthodox power system.

REFERENCES:REFERENCES:

• www.wikipedia.orgwww.wikipedia.org

• Power circuit breaker theory and Power circuit breaker theory and design bdesign by C.H. Flurscheimy C.H. Flurscheim

ANYANY

QUESTIONS?QUESTIONS?