In the power industry, SF6 is an important medium, which is used as the arc extinguishing and marginal gas for closed, high-voltage switches. The superior performance of sulfur hexafluoride gas realizes the economical and low-maintenance operation of the device. At present, as the edge and arc extinguishing medium, there is no other technology that can surpass SF6 gas from the technical, economic and ecological point of view.
Sulfur hexafluoride gas has been widely used in electrical equipment. From the application point of view, SF6 circuit breakers and GIS are important domains, which have basically replaced oil circuit breakers with voltages of 126kV and above. Obviously, it is an inevitable trend of development that SF6 gas replaces the edge oil as the arc extinguishing and edge medium.
From the chemical point of view, SF6 gas is not toxic, but when SF6 gas is used in electrical equipment, it forms toxic substances due to its interaction with high-temperature arcs. Metal materials and electrodes in power equipment will react with SF6 gas and its decomposition products to form toxic substances. At the same time, SF6 gas decomposition products will also react with the moisture in the power equipment, and will also form toxic substances. In addition, SF6 gas products lack a certain degree of purity. For example, SF6 gas contains hydrogen fluoride, low sulfur fluoride and other highly toxic gases when it leaves the factory. At the same time, it can be seen that the main source of toxicity is due to the impure SF6 gas and the emissions during chemical reactions. Once SF6 gas is used in power equipment, toxic gas leakage into the air will easily cause harm to human systems and the environment, so we must pay attention to the prevention of SF6 gas.
Harm to the environment. Although SF6 does not cause excessive harm to the ozone layer and air in the atmosphere, it is due to the chemical nature of SF6 gas. Once leaked into the air, it will remain for a long time, which will easily cause the problem of greenhouse effect and exacerbate global warming. As the society pays more and more attention to the issue of green environmental protection, in order to develop a green economy, most countries have formulated control measures for the safety of SF6 gas in industrial production and power equipment application, so as to reduce the probability of SF6 gas leakage. The degree of pollution to the atmosphere and the environment is minimized.
Hazard to the human body. One is that SF6 gas will carry certain other toxic gases or some toxic impurities that penetrate during the inflation process when leaving the factory. These certain toxic gases pose a certain hazard to the human body and threaten the personal safety of relevant operators.[3] The second is that when SF6 gas is used in power equipment, it releases toxic substances due to the chemical interaction of the gas with water, metal materials, and insulating materials in a high-temperature environment. Quite a part of the electrical equipment is in a sealed state, so the toxic gas cannot be discharged in time due to the restriction of the environment. When the maintenance personnel are exposed to these toxic gases during the maintenance, their health will be threatened.
Moreover, when SF6 gas contains moisture, it will cause the following hazards to electrical equipment:
(1) In the presence of moisture, SF6 decomposition products undergo a hydrolysis reaction, which hinders the recombination of SF6 decomposition products, reduces the recovery strength of SF6 media, and thereby reduces the feasibility of the equipment;
(2) Intensified hydrolysis of low fluoride and decomposition of metal fluoride. The generated fluorinated sulfurous acid and hydrofluoric acid are highly toxic, have great harm to the human body, and also corrode electrical and related materials;
(3) Condensation of sulfur hexafluoride gas in the equipment. Because the moisture in the gas exists in the form of water vapor, when the temperature drops, it may condense inside the equipment and adhere to the surface of the equipment such as electricity and edge surfaces. It is easy to produce creeping discharge (flashover) and cause accidents.