3.3 North Wales and the Midlands boundaries

The Western transmission region includes boundaries in Wales and the Midlands. The figure below shows likely power flow directions in the years to come up to 2030.

The arrows in the diagram are to illustrate power flow directions and, to an approximate scale, the flow magnitude in winter peak

Regional Drivers

Future offshore wind and biomass generation connecting in North Wales have the potential to drive increased power flows eastward into the Midlands where power plant closures are set to occur and demand is set to remain fairly high.

By 2035, the scenarios suggest a total amount of generation capacity of between 12GW to 24GW. At present, this region has significant levels of fossil fuel (about 20GW).

All scenarios show a decline in fossil fuel with slight growth in low-carbon technologies, interconnectors and storage.

The graph below shows that the gross demand as seen from the transmission network in the region will increase across all scenarios. This is driven by the adoption of technologies such as electric vehicles, heat pumps and embedded storage.

The graph shows that the gross demand as seen from the transmission network in the region will increase across all scenarios. This is driven by the adoption of technologies such as electric vehicles, heat pumps and embedded storage.

In a high decentralised scenario like System Transformation, local generation capacity connected at the distribution level in this western region could reach more than 49GW by 2040. Of that capacity, a typical embedded generation output on average might be around 20GW. This will vary depending on factors like wind speeds, and how other local generators decide to participate in the market.

Boundary Regions

Click on the regions below to expand the boundary and understand its capability and challenges.

If you would like to learn how to interpret the graphs, click the button below.

 

Interpreting boundary graphs

The graphs show a distribution of power flow for each scenario, in addition to the boundary power transfer capability and NETS SQSS requirements for the next twenty years. 

Each scenario has different generation and demand so produces different boundary power flow expectations. 

From applying the methodology in the NETS SQSS for wider boundary planning requirements (as discussed in section 2), we determine: 

  • the economy criteria - solid coloured line
  • security criteria - dashed coloured line
  • current boundary capability – solid black line

The current boundary capability is expected boundary capability for the coming 2020/21 year’s winter peak study. This will change over time as the network, generation, and demand change, all of which are uncertain and so a straight back line shows the present capability.

The calculations of the annual boundary flow are based on unconstrained market operation, meaning network restrictions are not applied. This way, the minimum cost generation output profile can be found. 
We can see where the expected future growing needs could be by looking at the free market power flows in comparison with boundary capability.

Using the B6 boundary charts as an example below, there are four charts – one for each of the scenarios in the FES.

On each graph, the two shaded areas provide confidence as to what the power flows would be across each boundary:

  • the darker region shows – 50% of the annual power flow or the 75th percentile in the range of power flows
  • the lighter region shows – 90% of the annual power flows or the 95th percentile in the range of power flows

From the regions, we can show how often the power flows expected in the region split by the boundary are within its capability (black line). 

If the capability of the boundary is lower than the two regions over the next 20 years, there might be a need for reinforcements to increase the capability. 

However, if the line is above the shaded regions, it shows that there should be sufficient capability here and that potentially no reinforcements are needed from a free market power flow perspective until the shaded regions exceed the capability (black line).

Close panel
Boundary B9 – Midlands to South of England

 

Boundary B9 separates the northern generation zones and the southern demand centres.

Developments in the east coast and the East Anglia regions, such as the locations of offshore wind generation connection and the network infrastructure requirements, will affect the transfer requirements and capability of boundary B9

Boundary Flows and Base capability

The boundary capacity is 12.5GW limited by a voltage constraint a fault on the Enderby–Ratcliffe on Soar double-circuit.

In all four scenarios, the requirements gradually increase to above the boundary capability for B9. The increase is more than last year showing a need for additional boundary capability in the future for three out of the four scenarios.

The generation expected behind B9 is a combination of offshore wind generation and biomass generation.

North Wales – overview

The onshore network in North Wales comprises a 400kV circuit ring that connects Pentir, Connah’s Quay and Trawsfynydd substations. 

A 400kV double-circuit spur crossing the Menai Strait and running the length of Anglesey connects the now decommissioned nuclear power station at Wylfa to Pentir. A short 400kV double-circuit cable spur from Pentir connects Dinorwig pumped storage power station. In addition, a 275kV spur traverses north of Trawsfynydd to Ffestiniog pumped storage power station. 

Most of these circuits are of double circuit tower construction. However, Pentir and Trawsfynydd within the Snowdonia National Park are connected by a single 400kV circuit, which is the main limiting factor for capacity in this area. The area is studied by analysing the local boundaries NW (North Wales) 1 to 3.

 

Boundary Regions

Click on the regions below to expand the boundary and understand its capability and challenges.

If you would like to learn how to interpret the graphs, click the button below.

Interpreting boundary graphs

The graphs show a distribution of power flow for each scenario, in addition to the boundary power transfer capability and NETS SQSS requirements for the next twenty years. 

Each scenario has different generation and demand so produces different boundary power flow expectations. 

From applying the methodology in the NETS SQSS for wider boundary planning requirements (as discussed in section 2), we determine: 

  • the economy criteria - solid coloured line
  • security criteria - dashed coloured line
  • current boundary capability – solid black line

The current boundary capability is expected boundary capability for the coming 2020/21 year’s winter peak study. This will change over time as the network, generation, and demand change, all of which are uncertain and so a straight back line shows the present capability.

The calculations of the annual boundary flow are based on unconstrained market operation, meaning network restrictions are not applied. This way, the minimum cost generation output profile can be found. 
We can see where the expected future growing needs could be by looking at the free market power flows in comparison with boundary capability.

Using the B6 boundary charts as an example below, there are four charts – one for each of the scenarios in the FES.

On each graph, the two shaded areas provide confidence as to what the power flows would be across each boundary:

  • the darker region shows – 50% of the annual power flow or the 75th percentile in the range of power flows
  • the lighter region shows – 90% of the annual power flows or the 95th percentile in the range of power flows

From the regions, we can show how often the power flows expected in the region split by the boundary are within its capability (black line). 

If the capability of the boundary is lower than the two regions over the next 20 years, there might be a need for reinforcements to increase the capability. 

However, if the line is above the shaded regions, it shows that there should be sufficient capability here and that potentially no reinforcements are needed from a free market power flow perspective until the shaded regions exceed the capability (black line).

Close panel
Boundary NW1 – Anglesey

Boundary flows and base capability

The boundary transfer capability is limited by the infrequent infeed loss risk criterion set in the SQSS, which is currently 1,800MW. If the infrequent infeed loss risk is exceeded, the boundary would need to be reinforced by adding a new transmission route across the boundary.

The generation expected behind NW1 is a combination of offshore wind generation and biomass generation.

In the System Transformation and Consumer Transformation scenarios in the FES, the requirements increase to above the boundary capability for NW1. The increase is more than last year suggesting a need for additional boundary capability in the future for two out of the four scenarios. 

Boundary NW2 – Anglesey and Caernarvonshire

Boundary flows and base capability

The boundary capability is thermally limited at 1.4GW for a double-circuit fault on the Connah’s Quay–Bodelwyddan–Pentir circuits which overloads the Pentir–Trawsfynydd single circuit.

Across all four FES scenarios, the SQSS economy required transfer grows beyond the present boundary capability. The expected power flows only grow beyond present capability from around 2029.

The scenarios show similar requirements until 2028 where they diverge due to different assumptions of connection time and dispatching of potential offshore wind and biomass generation behind this boundary.

Boundary NW3 – Anglesey and Caernarvonshire and Merionethshire

Boundary flows and base capability

The boundary capability is thermally limited at 5.5GW for a double-circuit fault on the Trawsfynydd–Treuddyn–Connah’s Quay tee circuits which overloads the Connah’s Quay–Bodelwyddan– Pentir tee circuits.

In all four scenarios in the FES, we see the SQSS economy required transfer grow beyond the present boundary capability.

The scenarios show a similar requirement until 2028 where they diverge due to different assumptions of connection time and dispatching of potential offshore wind and biomass generation behind this boundary