SEMINAR REPORT ON SWAGATIKA SAHOO REG NO:

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 under abnormal conditions

POINTS TO BE DISCUSSED:-  PRINCIPLE  ARCS  CLASSIFICATION  SF6 CIRCUIT BREAKER—DETAILS  CONCLUSION

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

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.

PRINCIPLES OF ARC EXTINCTION Factors responsible for arc:-  Potential difference between the contacts  Ionised particles between the contacts By removing any one of these the arc can be quenched.

CLASSIFICTION OF CIRCUIT BREAKERS OILAIR VACCUMSF6 OIL CIRCUIT BREAKER AIR BLAST CIRCUIT BREAKER VACCUM CIRCUIT BREAKER SF6 CIRCUIT BREAKER

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

1. Chemically inert 2. Non-toxic 3. Non-corrosive 4. Non-flammable Physical & Chemical properties 5. High density 6.High electro-negativity

Dielectric properties of SF6 gas:- DDS of sf6 is 2.5 times of air DDS of sf6 is 30% less than oil DDS of sf6 is equal to oil at N/m2 AAnd 15% higher at N/m2

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

SF6 CIRCUIT BREAKER OPERATION

SF6 DECOMPOSITION PRODUCTS S F6 SF4 + 2F SOF2 + 2HF MF n SO2 + HF SiF4 + 2 H2O SPARK H2O SiO2 M

 m agnitude & duration of discharge  m materials of construction of equipment  contamination levels of moisture and air inside the equipment Amount of each decomposition product depends on :-

REMOVAL OF SF6 BYPRODUCTS:- Byproducts are corrosive & likely to affect the organic materials. Absorbent materials used in circuit breakers  a activated alumina( effective for S OF2,H2S,SF2)  m 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

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

CONCLUSION Harnessing the utilities of SF 6 gas in power system and power system equipments, makes it more reliable and safer to use. The countless advantages this SF 6 gas has to offer will take us to new heights in the prevalent orthodox power system.

THANK U ALL FOR A PATIENT HEARING. HOPE I SATISFIED THE CURIOSITY OF THE AUDIENCE. NOW I WELCOME ALL QUERIES FROM MY REPORT.