The North South pylon line: How did we get here, where will it go?

by Jonathan F Dean

The long speculated north south pylon line seems to be on. Identified as critical to the U.K. government’s aim for clean power by 2030, necessary to get electricity from Scotland to south Wales and facilitating the mass building of onshore wind farms in mid Wales, National Grid are now offering connection agreements to it

How did we get here and where will it go?

The transmission grid in Wales

The electricity transmission system in Wales exists only in the north and the south. It’s more correct to say that some parts of the GB grid are in Wales, than to talk of a Welsh grid, as strictly speaking there is no Welsh grid, just some parts of the GB grid are in Wales

In the north, from the site of the decommissioned Wylfa nuclear power station a 400 kV line runs to Pentir near Bangor. From here it goes two ways – along the coast via Bodelwyddan to Connah’s Quay and through Eryri, via Trawsfynydd to Wrexham. Connah’s Quay and Wrexham link in with lines in England

In the south, from Pembroke power station, two lines run to Swansea North substation, where they go two ways – along the head of the valleys eventually to Walham substation in Gloucester and along to foot of the valleys eventually to Melksham substation east of Bath. These two are linked by Cilfynydd substation north west of Caerphilly

These two parts of the grid are connected to each other by a route around Birmingham and the midlands, and ultimately all other parts of GB. There are no transmission lines linking the two parts more directly through mid Wales – mainly because electricity demand there is so low, there is little generation, and they are not needed. But all that is about to change, the north will be connected to the south

Linking north to south

There have been tentative ideas to connect the transmission grid in north Wales to that in the south since at least 2009. Then the idea was a subsea connection from a new nuclear station at Wylfa to Pembroke. Also, back in 2012 National Grid Electricity Transmission (NGET) wanted to build a 400 kV transmission line from Lower Frankton in Shropshire to Cefn Coch, north west of Newtown, to service mid Wales wind farms. Neither of these happened when the generation projects were cancelled.

In 2020 the Offshore Transmission Network Review (OTNR) again suggested a subsea connection linking Lancashire to Wylfa to Pembroke, taking in new Irish Sea wind farms along the way

Offshore transmission has many plus points. It avoids every single wind farm having to send a cable to shore (termed radial connections) digging cable trenches each time, it avoids having substations in open countryside on agricultural land, as the cables only have to come ashore once, closest to where the electricity is needed, it needs less infrastructure overall and according to Ofgem will cost less

Linking north to south Wales also has merits, as it allows power from the Irish Sea to feed the south, or the Celtic Sea to feed the north. Mid Wales can always get sufficient power via the north and south distribution systems

But what about getting electricity from Scotland to England?

Scotland has vast resources for wind power. It can generate 2-3 times what it needs to reach net zero. Wales too could generate 150% of 2050 demand just from offshore wind. England though is deficient in renewables, so subsea cables are planned down the North Sea on the east coast and Irish Sea on the west coast. There is already a cable from Scotland into Deeside, and there is no reason why others could not come into Pembroke where the grid currently has lots of spare capacity to get power into England

However, the Holistic Network Design (HND) of 2022 didn’t do this. It brought power subsea from Scotland into Pentir (near Bangor) and took power from Pentir to Swansea North substation. Although heavily caveated as just indicating a network need, and not indicating a technology or route, it was described as a “double circuit” which basically means pylons, and Ofgem approved the pre-construction funding

In the “Beyond 2030” report earlier this year the National Energy System Operator (NESO) doubled the capacity of that in the HND, but interestingly showed the extra capacity connecting to Bodelwyddan not Pentir. NESO have since confirmed they are considering either, or both, landing points

Why the switch from offshore to onshore?

Although Wales can easily generate sufficient energy to reach net zero, and send an extra 50% to other parts of GB, from only offshore wind, there is a problem – Wales isn’t “allowed” to make decisions about the Welsh sea, only Westminster can do that. The previous U.K. government prioritised the North Sea, while the current U.K. government is still mulling things over. This left the Welsh government with onshore wind as the only option. Depending on how you view the Welsh Government they were either forced by an unresponsive Westminster or just don’t care about the Welsh countryside. Either way, the Welsh countryside is certainly “open for business” as far as onshore wind development goes

But there has always been a problem, the lack of a “collection” system to funnel all that energy to market. The wires on poles sufficient to get enough power in just aren’t sufficient to get power out. The need to connect Scotland to the south Wales grid was too good an opportunity to miss. Route those pylons through the middle of Wales and every other hill can have a wind farm, as there is an unending “thirst” for power in south east England (pun intended)

Mid Wales still doesn’t need any of this infrastructure, even though they are going to get it. The NESO projections for 2050 show mid Wales needs little more than a few 132 kV circuits on wooden poles to provide everything they need for net zero. What all of rural Wales needs is the distribution system upgrading – the wires on poles that get electricity to homes and businesses at lower voltages, but currently very little is being done about this. People in places like Builth Wells will be faced with the perverse situation of having wind farms and transmission lines but still not being able to get enough electricity for a heat pump or EV at home. Unfortunately this level of detail isn’t exciting enough for politicians and transmission, over which the Welsh government have no control, is frequently confused with distribution, over which the Welsh Government has some control

Where will the north south line go?

National Grid are still claiming that the north south project is “early days” and they are still considering all options, but there are facts emerging:

Bodelwyddan is fast becoming an energy hub with numerous offshore wind farms coming ashore there, as well as solar and storage projects and an interconnector to Ireland
A substation is planned at Gwyddelwern, near Corwen, for a number of onshore wind farms to the west near Bala (some right up to the boundary of Eryri national park) and battery storage (BESS)
The Mynydd Mawr proposed wind farm at Llanrhaeadr ym Mochnant to the west of Oswestry has been offered a connection agreement to the north south line (possibly at Gwyddelwern)
Scottish Power still have a project, started in 2011 but put on hold, for a substation at Cefn Coch near Llanfair Caereinion to the north of Newtown for several wind farms
The Carnedd Wen proposed wind farm near Mallwyd to the east of Dolgellau will connect to a substation called Mid Wales West but neither National Grid or Scottish Power will say where this is
The adjacent Esgair Ddu proposed windfarm (also up to the boundary of Eryri national park) doesn’t appear to have a connection agreement yet but will likely use Mid Wales West
Lightsource have a wind/solar/storage project called Berthlwyd that will connect to a substation called Mid Wales Connection Node A, but both the project and substation location is not clear, but could be near Newbridge on Wye
Swansea North substation is said to have no spare capacity and is spatially constrained by solar parks so cannot expand
A substation is planned at Llandyfaelog, south of Carmarthen, for several mid Wales wind farms as well as the Celtic Sea wind farms. This has had several names including Ferryside and Pont Abraham but is now known as South Wales West Connection Node C

In addition, the routing of overhead transmission lines has to be according to the Holford Rules contained in National Policy Statement EN-5 which includes:

Avoiding national parks and other designated landscapes – this would make Pentir a difficult starting point but cause no problems for Bodelwyddan
Using the most direct route possible
Using valleys as “transmission corridors” where pylons are not seen against skylines

Piecing all this together, a possible route for the line to take is; starting at Bodelwyddan head south down the Vale of Clwyd, Gwyddelwern, Cefn Coch, once near Builth Wells head south west down Dyffryn Tywi to Llandyfaelog. Bingo! The north is connected to the south

No doubt National Grid are busy offering connection agreements to the line so that when there is the eventual public outcry they can claim to be contractually bound to provide it

Personal thoughts and feelings

I have long been an advocate for renewables but also the right infrastructure in the right place. Routing pylons, yesterday’s technology to solve tomorrow’s problems, through the Welsh countryside, where there has never been such industrial structures, feels instinctively wrong, although I’m sure many of National Grid’s engineers are very excited

If there wasn’t the misguided desire to extract wind power from inner Wales, the alternative could be far simpler and elegant, a subsea HVDC “bootstrap” linking Pentir to Pembroke, as was proposed fifteen years ago

We can achieve net zero using only offshore wind. The Irish Sea alone can produce more energy than the whole of onshore Wales. We can transmit the energy long distances under the sea. We can get the energy to even the remotest farm using wooden poles or “ploughed in” cables. We can protect and conserve our landscapes for future generations. Everything is possible, but we’re not doing it

Instead we are littering our hills and moorlands with industrial wind farms, and stringing them all together using 55 m high steel lattice pylons. North Wales will literally be surrounded by a “ring of steel”

More offshore wind farms will come, in time, as will the subsea cables, as the U.K. needs the energy, but it’ll be too late to save the Welsh countryside. It makes me sad, angry but most of all betrayed, as the promise of new technology is once again being missed

Connecting the electricity transmission systems of north and south Wales

The long speculated plan seems to be on. Identified as critical to the U.K. government’s aim for clean power by 2030, necessary to get electricity from Scotland to south Wales and facilitating the mass building of onshore wind farms in mid Wales, National Grid are now offering connection agreements to it