What are the properties of sulfur hexafluoride (SF6) gas?- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

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What are the properties of sulfur hexafluoride (SF6) gas?

发布时间：2018-09-05 来源：ydlcb 浏览次数：38次

Sulfur hexafluoride is a century-old gas, which was synthesized by two French chemists, Moissan and Lebeau, in 1900 and made commercially available in 1947. At present, sulfur hexafluoride gas is mainly used in the power industry. Sulfur hexafluoride gas is used in four types of electrical equipment as insulation and/or arc suppression: sulfur hexafluoride circuit breakers and GIS, sulfur hexafluoride load switchgear, sulfur hexafluoride insulated transmission lines, sulfur hexafluoride transformers and sulfur hexafluoride insulated substations. From the point of view of gas consumption, 80% is used for high and high voltage power equipment. Since the 1960s, sulfur hexafluoride has been successfully applied to high voltage switchgear as an insulating and arc extinguishing medium. Sulfur hexafluoride is not only used in sulfur hexafluoride high-voltage electrical switchgear, but also used in sulfur hexafluoride transformer, sulfur hexafluoride transformer, sulfur hexafluoride lightning arrester, sulfur hexafluoride gas-filled cable and other high-voltage electrical equipment.

Sulfur hexafluoride has excellent arc extinguishing and insulation properties. Through decades of application practice, it has been proved that no other medium can be comparable, and it is expected to be irreplaceable in the next few decades.

Properties of sulfur hexafluoride gas

one Excellent performance of sulfur hexafluoride gas

Sulfur hexafluoride gas is suitable for power equipment, mainly has the following characteristics: strong electronegativity, with excellent arc extinguishing performance; High insulation strength, 3 times that of air at atmospheric pressure;

Good heat conductivity and easy recombination, especially when sulfur hexafluoride gas dissociates due to discharge or arc action; It can be stored in a small gas tank, because it is easy to liquefy at high pressure at room temperature; The gas supply is convenient, the price is not expensive and stable.

2. Chemical properties of sulfur hexafluoride gas

The main chemical properties of sulfur hexafluoride gas are shown in Table 1.

Table 1 Main chemical properties of sulfur hexafluoride
Molecular formula	Sulfur hexafluoride
Molar mass	146.05 g/mol
Sulfur content	21.95% (1)
Fluorine content	78.05% (1)
Molecular structure	An octahedron with fluorine atoms on six edges
key	Covalent bond
Collision cross section	4.77 A
Decomposition temperature	500 ℃
① refers to the mass score

Physical properties of sulfur hexafluoride gas

Sulfur hexafluoride is one of the most important known gases. Under normal conditions, it is about five times heavier than air. Under conditions of inadequate mixing with air, the gas tends to accumulate in low places. Mixed slowly with air by convection and diffusion, but once mixed, no longer separated. Although the thermal conductivity of sulfur hexafluoride gas is low, due to its low viscosity and high density, the total thermal conductivity is 2 to 5 times better than that of air. In power transmission and distribution equipment, the usual pressure range of sulfur hexafluoride is between 0.1MPa and 0.9MPa (absolute pressure).

Table 2 Main physical properties of sulfur hexafluoride at pressure 0.1MPa and temperature 25℃
density	6.14㎏/ m3
Thermal conductivity	0.013 W/(m • k)
Critical point
temperature	45.55 ℃
density	730㎏/m3
stress	3.78MPa(insulation pressure)
Velocity of sound	136m/s
Refractive index	1.000783
Heat of formation	1221.66 J/mol
Specific heat at constant pressure	96.60 J/mol • k)
State equilibrium	See Figure 1

As mentioned above, sulfur hexafluoride is a very stable and inert gas that is colorless, tasteless, non-toxic, non-flammable, and insoluble in water. It is one of the least reactive gases known, and under normal conditions it does not erode substances that come into contact with it.