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The growth of SF6 and suitable monitoring solutions

04 February 2020

THE RECENT drive for electrification has led to a dramatic increase in the use of Sulphur Hexafluoride (SF6). A dielectric gas, SF6 is used to prevent short circuits and catastrophic incidents within the electrical industry.

Despite its desirable electrical insulation properties, SF6 is a highly potent greenhouse gas with a global warming potential (GWP) 23,500 times greater than that of CO2.

In a bid to reach targets set to combat climate change, we are seeing a large increase in the number of sustainable forms of energy such as wind, solar and gas. In turn, this has driven an increase of SF6 usage in high voltage applications such as switchgears and circuit breakers. The benefits of using SF6 include excellent insulation, non-inflammable and chemical stability, minimum maintenance, outstanding arc quenching properties and reduced electrical clearances. 

So, where’s the catch? In 2017 within the EU alone, emissions of SF6 cost the climate the equivalent of putting an extra 1.3 million cars on the road. A study from the University of Cardiff found that across all transmission and distribution networks, the amount of SF6 used was increasing by 30-40 tonnes per year. The global installed base of SF6 is expected to grow by 75% by 2030.

According to a recent BBC article, the most important means by which SF6 gets into the atmosphere is from leaks in the electrical industry. A sustainable replacement for SF6 is unlikely to be made available anytime soon, however actions can be taken to ensure better gas monitoring and management to reduce SF6 leakage. 

SFoccurs naturally in trace quantities in sulphur- and uranium-bearing rocks, but the SFused commercially is man-made. SFis widely used by the electricity industry across the world in medium and high voltage switchgear and circuit breakers, because it is extremely effective as an electrical insulator and for quenching electric arcs. Some of the key advantages of SFover compressed air or oil in such applications are longer equipment lifetime, reduced maintenance and better reliability. SFalso poses no risk of land or water contamination, as oil-filled equipment does.

Arced SF6 gas is poisonous and with imperfect joints leading to leaks of SF6, continuous monitoring is essential. Being odourless and colourless, replying on human senses alone in, for example, an electrical power station, medical environment or semi-conductor manufacturing plant to detect SF6 is not accurate enough and potentially very dangerous. So a technical solution to monitoring traces of SFmust be used.

In its pure state SFis inert, colourless, tasteless, non-flammable and non-toxic. It is heavier than air and can accumulate in cable trenches, pits and tunnels. A volume grater than 19% in the air can cause asphyxiation. An appropriate risk assessment should be undertaken in order to determine if work areas are classified as confined spaces. In addition, the toxic solid by-products of SF6 which form fine powders such as aluminium fluoride (AlF3), copper fluoride (CuF2), and wolfram oxide (WO3) can be present as a result of interaction with Teflon, copper and tungsten contacts, and aluminium from shields. These fine powders are toxic if ingested or inhaled, causing eye, nose and throat irritation, pulmonary oedema, and other lung damage, skin and eye burns, nasal congestion, bronchitis, and rashes.

Dependent on the application there are a range of monitoring solutions available. Shawcity offers handheld, portable and continuous fixed monitoring solutions for applications ranging from spot checks through to accurate measurement. Using negative ion capture (NIC) our devices can measure leaks as low as 1 x 10-8ml/sec, with no need for carrier gases or radioactive sources. Fortunately, basic SF6 monitoring can be as easy as ‘switch on and go’. Contact us for further information or to discuss your requirements.

For more information, visit www.shawcity.co.uk