Insulation materials of SF6 electrical equipment
The internal insulation materials of SF6 electrical equipment include SF6 gas and solid insulation material. SF6 is commonly found in all SF6 electrical equipment; while the solid insulation material varies in different equipments, they are mainly thermal ethoxyline resin, polyest nylon, Polytetrafluoroethylene (PTFE), PVC, insulation paper and insulating varnish.
2.1 Gaseous insulating material-SF6 gas
SF6 gas is a stable, noncombustible and non-explosive matter that does not react at all under normal temperature and pressure. SF6 gas has strong electronegativity with pretty good insulation performance and arc extinguishing performance and it is the ideal insulation medium at present. It has been widely used as electrical insulation medium since the last 70s, having the functions of insulation, arc-extinguishing, cooling and heat dissipation.It breaks up when the temperature exceeds 500℃, evidently decomposes above 700℃ and quickly decomposes into mainly SO2, SOF2 and HF under arcing effect
2.2 Solid insulation material
They are mainly thermosetting epoxy resin, polyester nylon, PTPE, PVC, insulation paper and insulating varnish that are composed of C, H, F, O and N; Thermosetting epoxy resin mainly decomposes into SO2, H2S, CO, NO, NO2 and small amount of low molecular hydrocarbon when the temperature is above 500℃; PTFE mainly decomposes into CF4 and CO when the temperature is above 400℃; PVC, insulation paper and insulating varnish begin to decompose evidently when the temperature is 130℃, and the main products are H2,CO,CO2and low molecular hydrocarbon.