Sulphur hexafluoride (SF6) is a man-made gas comprising of one sulphur and six fluoride atoms. SF6 is extremely chemically stable, non-flammable and highly electronegative, with an excellent dielectric property of approximately 2.5 times more than air.
Therefore it is commonly used within electrical switchgear, transformers and substations as an electrical insulation, arc quenching and cooling medium.
Electrical arcs are a discharge of light and heat and can be caused within electrical power systems such as switchgear, when conductive channels facilitate their formation. The high electronegativity and heat transferring properties of SF6 means that it is able to absorb the electron energy and lower the arc temperature through the capture of free electrons. Combination of the SF6 gas and free electrons results in big, heavy ions with low rates of mobility, which effectively prevents electron avalanches and flashovers.
While under the influence of electrical discharges SF6 partially decomposes, separating into its atomic components. During this time oxygen, moisture and decomposition products such as sulphur dioxide may be created. Unlike other insulating mediums, SF6 gas has the unique ability to ‘self-heal’ with the atoms recombining after the discharge, this is one of the reasons for its widespread use within the electrical industry.
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