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Exemption certificate: pressure systems forming an enclosure for high voltage equipment

The exemption issued by the HSE entered into effect on 1 December 2021 and will remain in force for five years, when it will be reviewed. The exemption is applicable to any pressure system containing an insulating and interrupting gas and forming an integral part of high voltage (HV) electrical apparatus.

The Pressure System Safety Regulation 2000 (PSSR) aims to guarantee safe design and use of pressure systems, including high voltage pressurised units, that form part of the electrical network across the UK, and that are critical to maintaining supply. Current regulations include an exception, which effectively exempts application of PSSR to high voltage apparatus which have been manufactured to remain sealed, and which contain Sulphur hexafluoride (SF6). SF6 is an extremely potent and persistent greenhouse gas, with warming potential 23,900 times that of CO2 and with atmospheric residence of up to 3,200 years. The use of SF6 is facing increasing restrictions and potential international bans, prompting leading manufacturers to develop new designs of high voltage electrical apparatus using alternative gasses with significantly lower global warming potential.  

 This exception is extended to include other gases which meet the same technical and safety criteria offered by SF6.

  The exemption brings Pressure System Safety Regulation 2000 into line with Pressure Equipment (Safety) Regulations 2016 which also excludes all enclosures for high voltage electrical equipment regardless of the gas used.   Owners and operators of existing high voltage electrical equipment containing sulphur hexafluoride should ensure its integrity and safe operation by continuing to ensure that equipment is maintained and regularly inspected and tested in accordance with manufacturer’s instructions.   HSE expects that any new high voltage electrical equipment utilising alternative gasses will be designed, manufactured and tested to appropriate standards before being placed on the market. Owners and operators will also need to ensure that this new equipment is maintained and regularly inspected and tested in accordance with manufacturer’s instructions.

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