SF6 gas was first synthesized in 1900 and its insulating properties were discovered in the 1930s. It began being used commercially in electrical equipment in the 1940s due to its excellent dielectric properties. SF6 is highly electronegative and stable at high temperatures, allowing it to effectively quench arcs and dissipate heat in equipment like circuit breakers and switchgear. Its non-toxic and non-flammable qualities also make it safer than other insulating gases. SF6 quickly became the preferred gas for insulating high voltage equipment due to these advantages.

1. SF6 Gas

2. History of SF6
• SF6 or sulfur hexafluoride gas molecules are combined by one sulfur and six fluorine
atoms. This gas was first realized in the year 1900 in the laboratories of the Faculte de
Pharmacie de, in Paris. In the year of 1937, General Electrical Company first realized that
SF6 gas could be used as gaseous insulating material. After the Second World War, i.e. in
the middle of 20th century, the popularity of using sulfur hexafluoride gas as an insulating
material in electrical system was rising very rapidly. Allied Chemical Corporation and
Pennsalt were the first American industries, who began to produce this gas commercially
in 1948. During 1960, using of sulfur hexafluoride gas in high voltage switchgear became
popular. As the demand for this gas was increasing, many manufacturers in Europe and
America started producing SF6 gas in large scale, during that time. In the beginning, SF6
gas was only used for the insulating purpose in the electrical system. But soon it was
realized that this gas has tremendous arc quenching property. Hence, this gas also began
to be used in circuit breaker as arc quenching medium. World’s first SF6 gas insulated
substation was established in Paris in the year 1966. Sulphur hexafluoride medium
voltage circuit breakers launched into the market from 1971.

3. Physical &Chemical properties of SF6
• 1.Sulfur hexafluoride gas is very stable gas and remains stable up to 500 ℃.
• 2.SF6 is inert. The chemical inertness of this gas is advantageous in switchgear.
• The life of metallic part and contacts is longer in SF6 gas. The components do
• not get oxidized or deteriorated. Hence the maintenance requirements are
• reduced.
• 3.Sulfur hexafluoride gas is electronegative gas.
• 4.During arc extinction process SF6 is broken down to some extent into SF4 and
SF2. The products of decomposition recombine upon cooling to form the original
gas.
• 5.The metallic fluorides are good dielectric materials hence are safe for electrical
• equipment.

4. Physical &Chemical properties of SF6
• it is non flammable
• it is non toxic

5. 3. Why is SF6 gas such a good dielectric medium?
• First, dielectricity is the ability to transmit electricity without conductivity,
and dielectric strength refers to how well something can withstand high voltage
without breaking down. Electronegativity is the ability to capture free electrons,
and fluorine is the most electronegative element known on earth. 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.

6. Why is SF6 used in electric power equipment?
• Because of its outstanding electrical, physical and chemical
properties enabling significant benefits for the electricity supply
network:
• 1.It insulates 2.5 times better than air (N2),
• 2.Over 100 times better arc quenching capability than air (N2), and
• 3.Better heat dissipation than air;

7. What are the benefits of high and medium voltage
SF6-switchgear?
• Local operator safety
• Very high operational reliability
• Important contribution to the security of supply
• Small space requirement
• Excellent economical and ecological features

8. What are the most common applications of SF6 gas in
electrical power?
• Circuit breakers
• Switchgears
• Power, voltage, and current transformers
• Gas-insulated lines
• Capacitors

9. In what other industries are SF6 gas used?
• Besides electrical T&D applications, SF6 is commonly found in radiological
instruments, particle accelerators, equipment for semiconductor production, and
magnesium and aluminum casting. It is also used as insulation in windows to
dampen sound, and as a tracer gas in mining.

10. Why is SF6 the preferred insulator for breakers and
switchgears?
• 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.
In addition, equipment insulated with SF6 has lower operating noise,
does not emit hot gases, and require relatively little maintenance.