3.4 East of England Boundaries

The East of England region includes the counties of Norfolk and Suffolk. The figure below shows likely power flow directions in the years to come up to 2030

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

Regional Drivers

With the large amount of generation contracted to be connected in the area, predominantly offshore wind, nuclear and interconnector developments, the supply may significantly exceed the local demand which could cause heavy circuit loading, voltage depressions and stability issues.

Regional drivers

The future energy scenarios highlight that generation between 7 and 25GW could be expected to connect within this region by 2035. 

All scenarios show that, in the years to come, large amounts of low-carbon generation, predominantly wind, can be expected to connect. Fossil fuel generation can also be expected to connect within this region as well as an interconnector. The total generation in all the scenarios will exceed the local demand; thus the East of England will be a power exporting region.

The East Anglia transmission network to which the future energy scenarios generation will connect has eight 400kV double circuits. The potential future increase in generation within this region could force the network to experience very heavy circuit loading, stability issues and voltage depressions – for power transfer scenarios from East Anglia to London and south east England. This is explained as follows:

  • The East of England region is connected by several sets of long 400kV double circuits, including Bramford Pelham/Braintree, Walpole–Spalding North/Bicker Fenn and Walpole–Burwell Main. 

    During a fault on any one set of these circuits, power exported from this region is forced to reroute. This causes some of the power to flow through a much longer distance to reach the rest of the system, predominantly the Greater London and south east England networks via the East Anglia region. 

  • Stability becomes an additional concern when some of the large generators connect, further increasing the size of the generation group in the area connected to the network. 

    Losing a set of double circuits to a fault will lead to significant exposure to a risk of instability as power transfer increases.

The graph below shows snapshots of the peak gross demand for the East of England across the four different scenarios. 

 Peak gross demand in the East of England region is expected to be around 5-7GW by 2040. 

In a highly decentralised scenario like Leading the Way, local generation capacity connected at the distribution level in this eastern region could reach more than 15GW by 2040. Of that capacity, a typical embedded generation output on average might be around 4.8GW. This will vary depending on factors like wind speeds, and how other local generators decide to participate in the market. 

The NOA 2020/21 will assess the likelihood and impact of the above mentioned potential scenarios and accordingly recommend preferred reinforcements for the East of England transmission region.

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 EC5 – East Anglia


Boundary flows and base capability

The boundary capability is currently a voltage compliance limit at 3.5GW for a double-circuit fault on the Bramford–Pelham and Bramford–Braintree–Rayleigh Main circuits causing low voltage at Burwell Main substation.

The coastline and waters around East Anglia are attractive for the connection of offshore wind projects, including the large East Anglia Round 3 offshore zone that lies directly to the east. 

The existing nuclear generation site at Sizewell is one of the approved sites selected for new nuclear generation development. A new interconnector project is also contracted to connect within this boundary.

The growth in offshore wind, nuclear generation and interconnector capacities connecting behind this boundary greatly increase the power transfer requirements. The present boundary capability is sufficient for today’s needs but could be significantly short of the future capability requirements.