Byproducts in the Insulating Gaseous Matrix of a Gis
Sulfur hexaflouride (SF6) is a man-made gas, offering excellent electrical, thermal, and acoustical insulation properties, and as such, it has been extensively employed for a variety of applications, i.e. power distribution (mainly), semiconductor foundries, metallurgy, tracer gas, sound sealing (double glazing, torpedo noise silencer), thermal sealing, diving equipment, aeronautical, wind tunnels, telecommunications, relays, antennas, medical (ultrasounds, ophthalmology) etc1 . However, SF6 has been identified to be one of the strongest greenhouse gases, having a global warming potential 25000 greater, compared to that of CO2, and an exceptionally long lifetime (estimated between 1800 and 3200 years). SF6 is primarily employed worldwide (approximately 80% of its total production) as a gaseous insulator for high-voltage systems (GIS) including switchgear, gas insulated transmission lines, and power transformers. The current trend is to reduce SF6 quantities within electrical equipment by mixing it with natural gases. As a result, the interest for possible SF6/gas mixtures for power applications has been reignited. Most of the research work is now focused on SF6/N2 gas mixtures2, as it appears to be suitable for industrial non uniform electric field applications, combining environmental compatibility with comparable dielectric performance of pressurized SF6 and overall cost effectiveness. Other possible mixtures of SF6 that have been recently proposed are the SF6/CO2/N2 instead of the SF6/CO2 mixtures for transformer applications, and also, SF6 with dielectric mixtures of CHF3 and CF4 diluted at 50% to 75% with N2 for possible applications at lower temperature environments, thus combining environmental compatibility with reduced gas decomposition rates3.
KeywordsCorona Discharge Sulfur Hexafluoride Metal Fluoride Secondary Electron Multiplier Great Athens Area
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