SF6 gas and its use within high voltage applications - Part 1

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.

Regular analysis of SF6 gas is essential as part of a maintenance schedule. In order to protect personnel and equipment it is advised that periodic servicing is carried out throughout the lifetime of the equipment. Identification of elevated decomposition levels will ensure unnecessary inspections, outages and failures in addition to reducing maintenance expenditure and ensuring the effectiveness of the SF6 gas.

The Kyoto Protocol is an international agreement between nations that came into force in 2005. It commits its parties by mandating country-by-country reductions in greenhouse gas emissions. Under the Kyoto Protocol, SF6 gas has been identified as a greenhouse gas with a limitation as to the amount that can be released into the atmosphere. Stricter legislation has seen changes to the requirements of the electrical power industry in relation to the handling of SF6 gas.