Sulfur hexafluoride gas has * * * insulation performance and arc extinguishing performance, and is widely used in circuit breakers, gas insulated composite appliances, gas insulated transformers, gas insulated transformers, gas insulated cables and other power transmission and transformation equipment.

The pure sulfur hexafluoride gas is colorless, tasteless, non-toxic, nonflammable, and stable in physical and chemical properties under normal temperature and pressure. However, if there are partial discharge, reburning, and severe overheating faults in the equipment, the gas will decompose and produce harmful compounds such as SO2, H2S, CO, which will not only reduce the insulation performance of sulfur hexafluoride electrical equipment, but also seriously threaten personal safety.

The chemical property of sulfur hexafluoride gas is extremely stable. Its self decomposition temperature is above 500 ℃. Under normal operation conditions, there are few decomposition products. However, under the action of arc, spark and corona discharge, the gas will decompose and produce some low fluoride compounds, which will further react with electrode materials, insulation materials, water and oxygen to generate very complex compounds.

Sulfur hexafluoride gas does not decompose when its chemical property is below 500 ℃, but will decompose when its temperature exceeds 700 ℃; In addition, it will also decompose under the action of electric arc. SF4, SOF2, SO2F2, etc. are the decomposition gases of sulfur hexafluoride gas, which are active substances and generate hydrofluoric acid (HF) with the water left in electrical equipment. HF not only corrodes metal components, but also corrodes insulating materials, causing insulation damage.

The insulating materials used for sulfur hexafluoride electrical equipment are generally epoxy resin, unsaturated polyester, polytetrafluoroethylene plastic and winding polyester insulating parts. The corrosion of glass fiber reinforced resin matrix composites includes both physical corrosion and chemical corrosion: due to the adsorption of resin and sulfur hexafluoride, medium molecules enter the resin matrix through penetration and diffusion, causing the resin to expand; Dielectric penetration leads to partial discharge, which leads to insulation damage.

With the destruction of the resin matrix, the medium penetrates into the interface between glass fiber and resin, reducing the adhesive force between resin and fiber. HF and silicon dioxide (SiO2) in the glass fiber generate silicon tetrafluoride (SiF4), and then generate fluorosilicic acid (H2SiF6), which degrades the dielectric properties of high-purity sulfur hexafluoride. For the influence of sulfur hexafluoride decomposition gas on insulating materials, the order of material stability is ester group>amino group>acetal>silicon containing materials.

The content of the article comes from sulfur hexafluoride gas: http://www.feiliergas.com