Dielectrics used within electrical equipment must possess certain characteristics such as; provide thermal conductivity to dissipate heat, have excellent insulating properties to quench arcs, be chemically stable and have a low toxicity. SF6 gas is unique in that it meets all the stated requirements and is therefore an essential component within the power transmission and distribution network.
Arcing occurs within circuit breakers whenever they operate. This process causes the absorption and deceleration of electrons, which in turn causes partial decomposition of the SF6 gas. One of the main reasons why SF6 is used as an insulating gas is its ability to recombine the decomposition products and regenerate itself.
The early identification of any decomposition products or moisture within the SF6 gas will help avoid unnecessary shutdowns, outages and failures, in addition to reducing maintenance expenditure. In order to protect personnel, equipment and the environment regular SF6 analysis should be adopted within the maintenance schedule.
Stricter legislation has seen changes to the requirements of the electrical power industry in relation to the handling of 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. Due to the chemical stability of SF6 gas it has the potential to remain in the atmosphere for thousands of years. 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.
The following links provide further information into current environmental legislation and the correct use of SF6 gas within the electrical industry.