Presented by:
SWAGATIKA SAHOO

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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
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
OVERVIEW OF SF6 GAS:-
Dielectric properties of SF6 gas:-
 DS of sf6 is 2.5 times of air
 DS of sf6 is 30% less than oil
 DS of sf6 is equal to oil at 63700 N/m2
 And 15% higher at 122500 N/m2
Advantages of SF6 gas:-
SF6 CIRCUIT BREAKER
OPERATION
SF6 DECOMPOSITION PRODUCTS
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
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 SF6 gas 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.