Sizewell B

ECS helps EDF Sizewell remain SF6 compliant

EDF’s Sizewell B is a nuclear power station on the Suffolk coast. It is the UK’s only Pressurised Water Reactor.


Sizewell B’s total supply to the national grid is 1198 MW.


As sulphur hexafluoride (SF6) is a highly effective electrical insulator for high-voltage electrical applications, it's often used by power plants in their high-voltage circuit breakers. Sizewell B power station required emergency SF6 gas works to be completed on several gas zones within the plant.

The station’s transformer was part of a ‘planned outage’ where we need to ‘switch off’ parts of network for maintenance work, with the circuit due to be returned to service. However, the gas zones’ SF6 quality did not comply with mandatory IEC Standard 60480, the circuit was declared unacceptable and it could not resume service as scheduled. If not dealt with quickly and efficiently, EDF Sizewell B were at risk of incurring high cost through significant levels of lost generation.


Engineering and Consultancy Solutions (ECS) were contacted regarding this issue, and our SF6 experts were immediately brought in to support EDF. The first part of the work comprised setting to work to remove the non-compliant gas from the affected zones, followed by a deep clean. Oxygen Free Nitrogen was then introduced to dry the zones out, while avoiding any potential contamination. Finally, the gas zones were refilled, enabling EDF Sizewell B to resume service.


Ned Lee (EDF Electrical Programme Manager) praised ECS:

ECS have been very supportive in reacting to our issue of having to recondition the SF6 in a number of zones adjacent to Station Transformer 8. Nile was quick to react to the issue, support our need for detail and information and then understand our requirements and start making headway into securing resources and materials.

Another member of the EDF Sizewell B team added:

The programme was put together at very short notice and delivered safely and efficiently. I look forward to working with ECS on future projects.

National Grid Engineering & Consultancy Solutions can give your business an all-in-one contact to cover your SF6 needs. Our expert engineers provide SF6 leak detection surveys, gas leak repairs and top-ups for assets.

If you wish to discuss any aspect of our SF6 Survey and Top-up Service, please contact our Engineering & Consultancy Solutions team on: 0800 783 9228 or send an enquiry to [email protected].