How does a SF6 circuit breaker work?

How does a SF6 circuit breaker work?

In an SF6 Circuit breaker, sulphur hexafluoride gas is used as the arc quenching medium. The contacts of the breaker are opened in a high-pressure flow sulphur hexafluoride (SF6) gas and an arc is struck between them. The gas captures the conducting free electrons in the arc to form relatively immobile negative ions.

Why is SF6 used in circuit breakers?

Due to its low gaseous viscosity, SF6 gas can efficiently transfer heat by convection. Due to these unique properties of this gas, SF6 circuit breaker is used in a complete range of medium voltage and high voltage electrical power system.

What is the pressure of SF6?

The pressure of SF6 gas was determined to be 5.5 bar, which is typically used for SF6 circuit breaker. The other two gases have much lower dielectric strength than that of SF6 gas.

What happens to SF6 gas during arc extinction in SF6 circuit breaker?

SF6 circuit breaker is a type of circuit breaker in which sulfur hexafluoride gas or SF6 gas is used as the arc quenching medium. The current chopping phenomenon is less in SF6 circuit breaker and so the high reliability obtained. During arc extinction SF6 gets decomposed into SF4 and SF2.

What is the major drawback of using SF6 circuit breakers?

Sealing problems of the gas. Ingress of moisture in the gas system – dangerous. Deterioration of SF6 gas with time.

What is the purpose of SF6 gas?

Sulfur hexafluoride (SF6) /is/ used as an electrical insulating material in circuit breakers, cables, capacitors, and transformers .

Why is sulfur hexafluoride a good insulator?

SF6 has six fluorine molecules that can break away from sulfur, capture electrons during an arc, and then return to its original state. The gas’s electronegativity and high dielectric strength are why it is such a popular insulating gas for use in power T&D equipment.

What is the gas pressure of SF6 for a compressed gas insulated cable?

Rated SF6 gas pressure is unified at 0.6 MPa, gauge for all components.

How much pressure of SF6 gas is generally maintain in SF6 circuit breaker?

Types of SF6 Circuit Breaker As discussed, in 220 kV, 400 kV and 765 kV applications, the SF6 gas pressure is maintained at 6.5 bar.

What is the function of arcing horn in SF6 circuit breaker?

Arcing horns (sometimes arc-horns) are projecting conductors used to protect insulators or switch hardware on high voltage electric power transmission systems from damage during flashover.

Why SF6 provides better arc quenching?

SF6 is extremely effective at quenching the arc generated when switching or opening electrical circuits. It also has very high thermal conductivity, especially at high temperatures, and, therefore, dissipates heat much better than air, nitrogen, helium, or other gases.

How does a SF6 circuit breaker work in modern time?

The working of SF6 circuit breaker is a little bit different in modern time. The innovation of puffer type design makes the operation of SF6 CB much easier. In buffer type design, the arc energy is utilized to develop pressure in the arcing chamber for arc quenching.

How many interrupters do you need for SF6 CB?

Two interrupter SF6 CB applied for up to 420 kV (400 kV) system. Four interrupter SF6 CB applied for up to 800 kV (715 kV) system. The working of SF6 CB of first generation was quite simple and it is some extent similar to air blast circuit breaker.

What are the different types of SF6 CB?

There are mainly three types of SF 6 CB depending upon the voltage level of application- Single interrupter SF6 CB applied for up to 245 KV (220 KV) system. Two interrupter SF6 CB applied for up to 420 KV (400 KV) system.

Why is SF6 gas better for arc quenching?

Due to its low gaseous viscosity, SF6 gas can efficiently transfer heat by convection. So due to high dielectric strength and high cooling effect, SF 6 gas is approximately 100 times more effective arc quenching media than air.