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The national electricity transmission system (NETS) in East Anglia is encompassed by the EC5 boundary. The network in East Anglia was largely developed in the 1960s, built to supply regional demand, centred around Norwich and Ipswich. A large loop runs from Walpole in the north of the region to Pelham and Rayleigh/Tilbury in the south, via Norwich and Bramford.
The coastline and relatively shallow waters around East Anglia are attractive for the connection of offshore wind projects. The existing nuclear generation site at Sizewell is one of the approved sites selected for new nuclear generation development. New interconnector projects are also contracted to connect within this area.
The growth in offshore wind, nuclear generation and interconnector capacities connecting behind this boundary (a boundary splits the system into sections and shows where there are high-power transfers between parts of the network) greatly increase the power transfer requirements out of the region as local total generation will exceed local demand.
The existing high voltage electricity network in East Anglia does not have the capability needed to reliably and securely transport all the energy that will be connected while meeting the SQSS. Several network reinforcement projects are planned to address the shortfall of which Sea Link is one.
In addition to reinforcing the EC5 boundary, by connecting Sea Link into the NETS at the proposed Friston substation it also reinforces the Bramford-Sizewell radial circuits, which are due to carry additional power from offshore wind, new nuclear and interconnectors, so offering additional constraint savings to the consumer
The need in the South and East
The south of England transmission region includes boundaries LE1, SC1, SC1.5, SC2 and SC3. The LE1 boundary almost exclusively imports power from the north and west of England into the south-east.
Power flows in the region are determined by the need to meet domestic demand in the South East as well as imports and exports to Europe via interconnectors.
As more energy is pulled across London and into Kent, power flows across LE1 are set to increase.
Demand for electricity will grow; interconnectors will exchange more energy with European countries to help balance intermittent sources of power; and local generation in the region will reduce. As a result, the electricity transmission network in the South East will need to be reinforced to ensure it is able to continue operating safely and securely.
The Strategic Proposal
The network reinforcement needs identified in both East Anglia and the South East were reviewed together. A single solution which simultaneously dealt with both constraints was selected. The identified reinforcement that will help achieve this is an offshore 2GW HVDC link between Suffolk and Kent.