SF₆ Circuit Breaker

A fuse within which the present carrying contacts operate in greenhouse gas or SF6 gas is thought as Associate in Nursing SF6 fuse.
   SF6 has glorious insulating property. SF6 has high electro-negativity. meaning it's high affinity of interesting negatron. Whenever a negatron collides with the SF6 gas molecule, it's absorbed by that gas molecule and forms a negative particle. The attachment of negatron with SF6 gas molecules could occur in 2 alternative ways,
These negative ions clearly abundant heavier than a negatron and thus overall quality of the charged particle within the SF6 gas is far less as compared to different common gases. we all know that quality of charged particle is majorly answerable for conducting current through a gas.
Hence, for heavier and fewer mobile charged particles in an SF6 gas, it acquires terribly high nonconductor strength.
Not solely the gas includes a sensible nonconductor strength however conjointly it's the distinctive property of quick recombination when the supply energizing the spark is removed. The gas has conjointly excellent heat transfer property. thanks to its low vaporish consistency (because of less molecular mobility) SF6 gas will expeditiously transfer heat by convection. therefore thanks to its high nonconductor strength and high cooling impact SF6 gas is around one hundred times more practical arc conclusion media than air. thanks to these distinctive properties of this gas, SF6 fuse is employed in the complete vary of medium voltage and high voltage power system. These circuit breakers are out there for the voltage ranges from 33KV to 800 potential unit and even a lot of.
The SF6 gas is known as a gas, safety regulation is being introduced in several countries so as to stop its unharness into the atmosphere. Puffer kind style of SF6 CB desires a high energy that is nearly 5 times bigger than that of oil fuse.
There are chiefly 3 kinds of SF6 CB relying upon the voltage level of application-

• Single device SF6 CB applied for up to 245 KV(220 KV) system.
• Two devices SF6 CB applied for up to 420 KV(400 KV) system.
• Four devices SF6 CB applied for up to 800 KV(715 KV) system.

The operating of SF6 CB of initial generation was quite easy and it's some extent like air blast fuse. Here SF6 gas was compressed and keep in a very high reservoir. throughout operation of SF6 fuse this extremely propellent is discharged through the arc in the breaker and picked up to the comparatively low reservoir and so it's pumped-up back to the high reservoir to re-utilize.
The operating of SF6 fuse is no bit totally different in fashionable time. The innovation of puffer kind style makes the operation of SF6 CB abundant easier. In buffer kind style, the arc energy is employed to develop pressure within the arcing chamber for arc conclusion.
Here the breaker is stuffed with SF6 gas at the rated pressure. There are 2 mounted contacts fitted with a particular contact gap. A slippery cylinder bridges these to mounted contacts. The cylinder will axially slide upward and downward on the contacts. there's one stationary piston within the cylinder that is mounted with different stationary elements of the SF6 fuse, in such the simplest way that it cannot amend its position throughout the movement of the cylinder. because the piston is mounted and the cylinder is movable or slippery, the inner volume of the cylinder changes once the cylinder slides.
During gap of the breaker the cylinder moves downward against the position of the mounted piston thence the quantity within the cylinder is reduced that produces compressed SF6 gas within the cylinder. The cylinder has numbers of aspect vents that were blocked by higher mounted contact body throughout closed position. because the cylinder moves any downward, these vent openings cross the higher mounted contact, and become unblocked and so compressed SF6 gas within the cylinder can kick off through this vents in high speed towards the arc and passes through the axial hole of each mounted contacts. The arc is quenched throughout this flow of SF6 gas.
During closing of the fuse, the slippery cylinder moves upwards and because the position of piston remains at mounted height, the quantity of the cylinder will increase that introduces low within the cylinder compared to the encircling. thanks to this pressure distinction SF6 gas from encompassing can attempt to enter the cylinder. the upper-pressure gas can come back through the axial hole of each mounted contact and enters into the cylinder via vent and through this flow; the gas can quench the arc.