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SEMINAR REPORT ON

SEMINAR REPORT ON. SF6. CIRCUIT BREAKER. BRANCH-EEE. CONTENTS. Introduction Operating Principle of Circuit Breaker Over view of SF6(Electrical properties) Physical and chemical properties Advantage Principle of operation of SF6 CB Conclusion References.

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SEMINAR REPORT ON

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  1. SEMINAR REPORT ON SF6 CIRCUIT BREAKER BRANCH-EEE.

  2. CONTENTS • Introduction • Operating Principle of Circuit Breaker • Over view of SF6(Electrical properties) • Physical and chemical properties • Advantage • Principle of operation of SF6 CB • Conclusion • References

  3. WHAT IS A CIRCUIT BREAKER? A circuit breaker is an equipment which can • make or break a circuit either manually or automatically under normal conditions • break a circuit automatically under abnormal conditions

  4. Fixed contact Fixed contact ARC ARC IS QUENCHED BY MEDIUM ARC Moving contact Moving contact OPERATING PRINCIPLE OF BREAKER IN A CIRCUIT BREAKER

  5. OVERVIEW OF ARCS IN BREAKERS-: During the separation of contacts, due to large fault current and high current density at the contact region the surrounding medium ionises and thus a conducting medium is formed. This is called the ARC.

  6. PRODUCTION OF ARC Factors responsible for arc:- • Potential difference between the contacts • Ionized particles between the contacts By removing any one of these the arc can be quenched.

  7. OVERVIEW OF SF6 GAS:- Electrical properties 1. High dielectric strength 2. Excellent arc quenching ability 3. Excellent thermal stability 4. Good thermal conductivity

  8. Physical & Chemical properties 1. Chemically inert 2. Non-toxic 3. Non-corrosive 4. Non-flammable 5. High density

  9. Dielectric properties of SF6 gas:- • DS of SF6is 2.5 times of air • DS of SF6 is 30% less than oil • DS of SF6 is equal to oil at 650 gm/cm2 • And 15% higher at 1.25 Kg/cm2

  10. Advantages of SF6 gas:- 1. Increased safety 2. Reduced size 3. Easy installation 4. Low maintenance

  11. SF6 CIRCUIT BREAKEROPERATION

  12. SF6 DECOMPOSITION PRODUCTS SF6 SPARK SF4 + 2F H2O M SOF2 + 2HF MFn SiO2 H2O SiF4 + 2 H2O SO2 + HF

  13. Amount of each decomposition product depends on :- • magnitude & duration of discharge • materials of construction of equipment • contamination levels of moisture and air inside theequipment

  14. REMOVAL OF SF6 BYPRODUCTS:- Byproducts are corrosive & likely to affect the organic materials. Absorbent materials used in circuit breakers • activated alumina( effective for SOF2,H2S,SF2) • molecular sieves( sodalime-CaO.NaOH)-removes stable gases such as SF4,SiF4 & S2F2 So suggested mix is 50/50 of sodalime& alumina. The suggested weight of absorbent is 10% of the weight of the gas

  15. ADVANTAGES OF SF6 CIRCUIT BREAKERS • Very short arcing period • Can interrupt much larger currents as compared to other breakers • No risk of fire • Low maintenance, light foundation, minimum auxiliary equipments • No over voltage problem

  16. CONCLUSION Harnessing the utilities of SF6gas in power system and power system equipments, makes it more reliable and safer to use. The countless advantages this SF6 gas has to offer will take us to new heights in the prevalent orthodox power system.

  17. REFERENCES: • www.wikipedia.org • Power circuit breaker theory and design by C.H. Flurscheim

  18. THANK YOU

  19. ANY QUESTIONS?

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