One of the biggest safety challenges in the electric power industry is managing the risks posed by unwanted electrical discharges. With an increasing move towards renewable energy sources, such as solar, wind and biogas, there is a need for many more individual connections to the national electrical grid, which means the need for more switchgears. Switchgears contain a combination of fuses, switches, circuit breakers, etc., and can be used to switch on or off certain pieces of equipment, or, in the case of a fault, to de-energise equipment from the huge voltages handled at power stations.

One typical switchgear design, the gas-insulated switchgear, uses a refrigerant gas, sulfur hexafluoride (SF₆), as an insulator. Owing to its very large dielectric constant, SF₆, is a very good insulator and so it has found widespread use in switchgears that need very high voltage handling capabilities.¹ It is very chemically inert and therefore compatible with the materials used for building the switchgears, though SF₆ can form decomposition products in some environments, when equipment defects have started to occur.²

Switchgears using SF₆ insulators are typically particularly low noise, very low maintenance and can be used with very high voltages, which is what has led to the widespread use of SF₆-based switchgear designs.¹ However, there are some significant issues surrounding the use of refrigerant gases such as SF₆. SF₆ is a potent greenhouse gas, with a global warming potential 23,500 times that of carbon dioxide when compared over a one-hundred-year period and, like most of the chlorofluorocarbon (CFC) gases, it is incredibly persistent in the atmosphere, with an atmospheric lifetime of about 3200 years.³

Industrial Sources of SF₆

The long atmospheric lifetime of SF₆ and the lack of natural decomposition routes for it mean that SF₆ concentrations in the atmosphere have continued to rise. Concerns about its contribution to global warming and the lack of methods for removing it from the atmosphere led to an EU-wide ban on the use of SF₆ in 2014, with an exception for the electrical industry as it was considered there was not a suitable replacement chemical at the time.⁴ In order to try and monitor SF₆ usage, with a view to phasing out the use of the gas when possible, countries are now required to report their yearly usage to the UN, but atmospheric measurements suggest much larger quantities of the gas are being released than is reported.⁵

The main mechanisms of SF₆ leakage from the electric power industry are thought to be from old switchgear designs⁶, damaged equipment and errors with gas handling during installation, maintenance and disposal.⁷

Leak Monitoring and Control

With SF₆ being labelled by the Intergovernmental Panel on Climate Change (IPCC) as the most potent greenhouse gas they have ever evaluated, preventative measures to avoid leaks are essential.³ Alongside this, there is a huge need for online gas monitors capable of rapid and accurate detection of even very low concentrations of SF₆.

Edinburgh Sensors has extensive experience in the design and creation of OEM gas sensors. They offer a comprehensive range of devices based on nondispersive infrared (NDIR) technology, suitable for a range of gases, including carbon dioxide and a range of hydrocarbon species.⁸

For SF₆ monitoring, Edinburgh Sensors offer the Chillcard NG⁹ and the Guardian NG¹⁰. Both of these are robust, self-contained units that provide near-analyser quality continuous sampling.