SF6 is and artificial gas used in switchgear and installations. Sulphur hexaflouride is one of the strongest green house effect gas mentioned by the Kyoto protocol. It has a potential for global warming that is about 23 900 times bigger than carbon oxide, CO2.
Switchgear manufacturers use SF6 gas in order to build secure, reliable and compact installations for companies in the generation, transmission and distribution electric power industry.
It is used as a insulation medium for high voltage switcgear and apparatus due to its great arc quenching characteristics. |
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Discharges during manufacturing, installation, service and dismantling is a bigger problem than actual leaks from already installed products. It is important for the suppliers of theese types of products that the handling prevents disharges and secures a good recycling policy.
Most products contains SF6 products in closed systems that normally remains sealed throughout the products entire lifespan. As the product develop the leakrates decrease for each new generation.
The manufacturers, power companies and utilities need to make sure that the procedures surrounding SF6 are in accordance with recommendations from enviromental authorities. |
Several international organisations such as CIGRE, CAPIEL and NEMA also directs guide lines for these companies.
Despite the international science community's efforts over decades to find a more enviromental friendly version they have been unsuccessful. Globally we manufacture 7500 tons each year and approximately 25% of those are used in new electrical apparatus. The rest is basically used to compensate leakage in old electrical apparatus. The total global leakrate is 5000 to 6000 tons/year.
Since more than 40 years sulphur hexaflouride is used in the electricity industry as insulated and quenching medium for gas insulated substations (GIS) and circuit breakers (GCB). As stated previously ,even under ecological aspects there is no alternative to SF6 avalable until today (life cicle assessment). Arcing processes that belong to everyday’s operation of a GCB or partial discharge activity over a long period cause the decomposition of the SF6 to highly corrosive and toxic by-products. |
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These decomposition products react with the inner components of the equipment and reduce its surface stability so that even mayor breakdowns can become the consequence. The pre-requisite to form these decomposition products are reactants like water (H2O) and air (N2O).
Therefore organisations like the CIGRÉ (SF6-Recycling Guide), SOLVAY FLOUR (SF6 Producer) and the IEC 60480 recommend to regularily check the concentration of decomposition products as well as of moisture and the purity of the SF6 applying a condition based maintenance (CBM).
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