When network reinforcement gets personal…Part 1

The beginning

The Hinkley Connection Project will likely be known to many of you as the new 57km new 400kV line from Bridgwater (in Somerset) to the Avonmouth Docks area (to the west of Bristol), utilising the new T-pylon towers. It is required to allow the new 3.2GW Hinkley Point C nuclear power station to connect. With the new T-pylons having sprung up along most of the route, now is a good time for me to reflect on this project, as it has been a part of my professional life over the last 15 years.

Hinkley Point C, to be the UK’s first nuclear power station since Sizewell B started operating in 1995, was granted planning permission in March 2013. But even before the initial government announcement in 2010 on the future of Hinkley, initial plans for the new 400kV line through Somerset for Hinkley C were underway. I know, because I was involved.

I joined Western Power Distribution (now called National Grid Electricity Distribution) in 2007, a relatively junior engineer with six years’ experience. I hadn’t long been in post as a network design engineer when, in 2008, National Grid approached WPD to begin discussions about a new 400kV line through Somerset. The 132kV network in Somerset happened to be my ‘patch’, and so began a long and enjoyable (although not always straightforward) involvement in the development of the Hinkley C connection project.

Design process

I was heavily involved in the design and development of the proposals, which include removing?an existing 132kV overhead line and establishing a new Grid Supply Point (GSP) just outside the village of Sandford. Most of my work in the early days was developing the design of the network without the 132kV line. Was a new 400/132kV GSP required to replace the circuit? The answer was yes, so the next question was, what did the new network need to look like with the new GSP? Where would it go? How would it interface with the remaining network?

This work required multiple people from WPD and NGET, looking at multiple design options and parameters. We developed designs in conjunction with the delivery teams, to ensure they could be implemented. Once a concept had been developed, it would be tested with the control rooms and ops teams, who would help to refine the designs. Due to the long time scale of the project construction, multiple phases needed to be considered, not just the start and end points. Supplies to customers needed to remain secure throughout the duration of the works.

As enjoyable as the design works were, my favourite experience has to be participating in a local consultation event when, as the only member of the local DNO in the room, a gentleman was pointed my direction about a question in relation to his electricity supply. I was, of course, happy to help and said I would do my best to assist. It was at this point the man asked me why his toaster wasn’t working and what WPD was going to do about the supply to his house to fix it!

Delivery begins

It wasn’t a surprise in 2016 when the new 400kV overhead line, using the innovative T-pylons, was given planning permission, seeing as Hinkley C had already been granted planning three years earlier. When I moved on in 2017 to manage the South West design team and then in 2019 to manage all four design teams, I kept an overview of the project and saw it move into the delivery phase. It was great to see others stepping up and taking on the work and bringing their own skills to the task. And it’s always a great, if somewhat nerve-wracking, experience to see scheme designs actually delivered. The Hinkley C connection project has been a testament to great collaborative working between NGET, WPD and many others over a long period of time.

Looking forward

My first reflection on this project is that transmission reinforcement is highly complex. It involves interaction with multiple parties, including DNOs, contractors, regulators, government, local authorities, local communities, and many more. The technical designs overlay with issues of deliverability and visual impact to create a highly iterative process. As such, it is a significant drain on company resources to make it happen. But not only that, the skills and working relationships take time to develop. Most network engineers only get to experience large scale transmission reinforcement like the Hinkley Connection Project once or twice in their career, so there isn’t necessarily a large pool of transmission reinforcement-ready workforce waiting for their next job. The staff within the TOs and DNOs have the skills they need, but they often need time and space to develop it into an effective project team.

My second reflection is that transmission reinforcement takes a long time. Whilst the Hinkley Connection Project has inevitably been impacted by delays in the delivery of Hinkley C itself, it has taken the best part of 15 years to go from concept to delivery. During that time, multiple people have come and gone on the project, requiring careful handovers of designs and project management.

A quick look at NGESO’s Holistic Network Design from last year shows huge amounts of transmission reinforcement required to deliver all the contracted generation required to meet net zero targets. Some of this reinforcement involves new transmission circuits, many of which are longer than the new 400kV circuit through Somerset. For example, there is a new 400kV circuit required from the south Humber area to the Lincolnshire coast, and on down to the Wash. This is the best part of 100km and without the advantage of a ‘sacrificial’ 132kV circuit for much of the route. Customers with new transmission circuits as Enabling Works in their offers need to be wary of the real-world deliverability of these schemes.

My third reflection is that these projects are highly costly. NGET originally applied to Ofgem for over ￡700m to fund this project (although Ofgem reduced this to about ￡655m). With prices everywhere having risen significantly in recent years, and with the potential of limited contractor availability for competing transmission projects, prices for future works could be significantly more expensive in real terms.

Whilst transmission reinforcements are challenging, lengthy and costly, they are an crucial way of unlocking capacity on the network for the continued roll out of low carbon generation, to meet net zero and improve energy security.

In my next article, I will look at Hinkley Connection Project from the point of view of me as a local, living with the reality of a new transmission circuit almost on my doorstep.