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This project ended in May 2019 and is now closed.

SF6 Alternatives

Funding mechanismNetwork Innovation Allowance (NIA)
DurationMay 2017 - May 2019
Project expenditure400k
Research areaSafety, Health & Environment
  • South West
  • South Wales
  • West Midlands
  • East Midlands
  • November 2018

    The project has now closed.


The objectives of this project are to:

  1. Conduct a literature review on all previous research considering SF6 gas alternatives;
  2. Identify alternative solutions from the literature review which can be recommended for initial testing;
  3. Conduct initial interruption and insulation tests on the proposed gases and document outcomes; and
  4. Disseminate the lessons learnt to internal and external stakeholders.


Sulphur Hexafluoride (SF6) is an extremely potent greenhouse gas, the use of which is increasingly becoming restricted and regulated (2014 EU fluorinated greenhouse gases (F gas) regulations). This presents a significant problem to network operators as SF6 is an excellent insulating medium which is used extensively in High Voltage (HV) and Extra High Voltage (EHV) switchgear. 

Network operators are responsible for monitoring SF6 that is leaked into the atmosphere. A biannual check is currently stipulated in the regulations for switchgear containing more than 6kg of SF6. If the equipment contains more than 22kg of SF6 then checks require to be made every three months. The majority of HV switchgear contains less than 5kg of SF6, therefore checks are not mandatory; however, regulations are constantly changing and these levels could change in the future. 

The regulations were recently amended and a new requirement came into force on 1 January 2017. This new requirement stipulates that any new switchgear being installed with more than 22kg of SF6 must have an automatic leak detection system fitted. With SF6 regulations anticipated to increase further there may be a requirement for every new piece of switchgear to be equipped with leak detection technology in the future. This could result in expensive modifications and systems associated with managing leak detection. 

The increased expense in complying with future regulations may lead to higher consumer charges for electricity use.


The aim of this project is to evaluate alternative insulating medium in place of SF6. The initial phase of the project will involve a literature review to capture previous learning from other projects and research into SF6 alternatives. The literature review should capture all material properties of SF6 to form a basis for comparison of alternative gases and ultimately the selection of a range of the most suitable insulating mediums for test in the next stage of the project. Following the literature review, the next stage will involve identifying and assessing the alternatives that could be used to replace SF6. A selection of insulating mediums will be chosen for initial testing in SF6 switchgear (such as RMUs which have been removed from the system). The results from the testing trials shall be captured in the final phase of the project and recommendations made for transitioning into business as usual (BaU). 

It is anticipated that the development of an SF6 alternative will lead to environmentally friendly HV switchgear. The chosen solution will be applicable as an interrupting medium in gas-filled RMUs and insulating medium in indoor switchgear. 
As there is a high volume of SF6 11kV RMUs on most DNOs’ networks, the project will focus on these devices and specifically the retrofitting of an alternative interrupting medium to replace SF6. It is recognised that most 11kV primary switchgear does contain SF6 with most being air insulated with vacuum interrupters. EHV SF6 Gas Insulated Switchgear (GIS) may be investigated in a future project.