The network in East Anglia today
A large loop runs from Walpole in the north to Pelham and Rayleigh/Tilbury in the south, via Norwich and Bramford. Two 400,000 volt (400 kV) overhead lines connect Sizewell B, and a decommissioned 132,000 volt (132 kV) overhead line used to connect the now decommissioned Bradwell A nuclear power station. Historically there was relatively limited generation and low consumer demand in East Anglia when compared to other parts of the country.
Current generation and demand
The amount of generation in the region has historically been relatively low compared to other parts of the country.
Sizewell B provides nearly a third of the overall generation total for the region, whilst a substantial contribution also comes from offshore wind farms, such as Dudgeon off the Norfolk coast.
910 MW of generation also connects in the region via the UK Power Networks lower voltage distribution network.
All of these generation sources help keep the lights on for millions of people and power homes and businesses across East Anglia and beyond.
Demand for electricity in the region has been falling slightly in recent years. Peak demand on the network is forecast this year at 1,346 MW. However, demand across the UK as a whole continues to rise.
How power is transported
Each line of pylons on the network carries two electrical circuits. There are four circuits connecting to and from the region – two circuits on the overhead line between Walpole and Norwich to the north and two on the line running west out of Bramford to Twinstead Tee.
The network is planned and operated under a set of standards designed to ensure there are no widespread electricity supply interruptions, even if two circuits are out of service.
Taking the standards into account, the network today in East Anglia has around 3.5 GW of transfer capability out of the region, with two of the four circuits connecting the region to the wider network out of service.
The network as it is today has been able to meet the needs of the region and transfer power out of East Anglia, but with a huge increase in renewable and low carbon generation coming, that is about to change.
Moving towards net zero
As we move toward cleaner, greener sources of energy, and more of the energy we use comes from offshore wind, nuclear power, and trading energy through interconnectors with other countries across the North Sea, the demand on the electricity network is set to significantly increase.
The UK has set a world-leading target to tackle climate change, which is to achieve net zero carbon emissions by 2050.
The network in East Anglia will play a vital part in helping to meet this goal, with 60% of upcoming offshore wind generation set to come ashore along the east coast.
Future generation
While the network in East Anglia can accommodate the level of generation and demand that there is today, this situation will change over the next decade with the increase in the amount of electricity set to come from offshore wind, interconnectors and nuclear power.
By the end of this decade, there will be significantly more generation than the current network is capable of accommodating.
National Grid ESO assesses how much energy needs to be carried on the network in the future, and expects that the Eastern Region could see renewable generation capacity rise to between 10 GW and 17 GW in the next ten years.
Increasing the capability of the existing network
Before we consider building new parts of the network we first must consider whether we can achieve more capability by upgrading parts of the existing network.
In the first half of the decade that’s exactly what we will be doing.
We will be installing power control devices at key substations in the region – at Pelham, Rye House and Waltham Cross, to make more use of an existing route to the west of the region.
We will be increasing the voltage of a section of line from Waltham Cross south into London to 400kV to increase the capability of that part of the network on into the capital.
We will be re-wiring existing overhead lines with larger diameter conductors that can carry more power – for example on the existing overhead lines from Bramford to Braintree to Rayleigh to Tilbury.
Making these improvements increases the capability of the existing network to around 6 GW. But it is still insufficient to deliver up to 17.9 GW of export capability that the National Grid ESO advises is required to deliver cleaner, greener energy to homes and businesses beyond the region in line with Government ambitions.
These upgrades alone won’t provide enough additional capacity, so we also need to build new parts of the network between Bramford and Twinstead, a subsea link between East Anglia and Kent, and between Norwich in the north of the region to Tilbury in the south.
Reinforcing the network between Bramford and Twinstead
A new route is needed between Bramford and Twinstead Tee because there are three double circuit overhead electricity lines carrying power into Bramford – one from Norwich to the north and two from Sizewell to the east – but west of Bramford out to Twinstead Tee, there is only one carrying power out of the region.
With substantial new sources of energy connecting in the region by the end of the decade, the existing overhead line west of Bramford would be overloaded, which would fall short of the Security and Quality of Supply Standards.
Beyond Twinstead Tee there are two routes out of the region – one west to Pelham and one south to Braintree-Rayleigh-Tilbury. Adding a double circuit route between Bramford to Twinstead will remove that bottleneck on the network and make more efficient use of the two routes west and south of Twinstead Tee. Reinforcing the network between Bramford and Twinstead will create two independent double circuit transmission routes west of Bramford – one from Bramford to Pelham and one from Bramford to Braintree to Rayleigh to Tilbury.