The network today in East Anglia
Like much of the high voltage electricity transmission network across the country, the network in East Anglia was largely developed in the 1960s. It was built to supply regional demand, centred around Norwich and Ipswich, and fed from our Bramford substation.
A large loop runs from Walpole in the north of the region to Pelham and Rayleigh/Tilbury in the south, via Norwich and Bramford. Two 400 kV overhead lines connect Sizewell B, and an unenergised 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 with other parts of the country. In recent years, peak demand for electricity in the region has fallen slightly – from a peak of 1,426 MW in 2019 to 1,346 MW in 2021.
Current generation and demand in East Anglia
To understand current and future demands on the electricity network, the concept of network boundaries is used. A boundary splits the system into sections and shows where there are high-power flows between parts of the network. When flows across a network boundary are forecast to be above the capability of the network, there are two options to manage this:
Pay electricity generators on one side of the boundary to reduce the energy they produce (and in turn pay generators on the other side of the boundary to compensate for the shortfall). This then reduces the flows of electricity across the boundary. When National Grid ESO pay generators to do this, these are called ‘constraint payments’; and/or
Increase the capability of the network to allow more electricity to flow.
At present, generation in the region currently totals 4,100 MW. Most of this generation (3,160 MW) is directly connected to our network and 940 MW is connected via the UK Power Networks distribution network. We call the locally-connected generation ‘embedded’. This is shown in the table below.
*connected via the distribution network
The Security and Quality of Supply Standard
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.
Each line of pylons on the network carries two electrical circuits.
For example, if one circuit is switched out for planned maintenance and another is impacted by a fault at the same time, the Security and Quality of Supply Standard is designed to ensure:
electricity system frequency is maintained within statutory limits
no part of the network is overloaded beyond its capability
voltage performance stays within acceptable statutory limits
the system remains electrically stable.
National Grid ESO oversees the standards, and they are approved by a Security and Quality of Supply Standard panel and Ofgem.
Future generation and demand
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. New connections for new offshore wind and nuclear power generation projects and for interconnectors are expected into East Anglia by 2030. These are being constructed or expected into substations at Necton, Norwich Main, Bramford, Friston and Sizewell.
Additionally, agreements are in place with two offshore wind farm projects on the basis of their connection into the new East Anglia Connection substation (EAC).
National Grid has a duty to facilitate new connections and maintain a safe national transmission system.
Studies by National Grid ESO considered the capability of the existing network. They took into account the planned upgrades to existing circuits and the proposed Bramford to Twinstead Reinforcement. The assessments, in line with the analysis of credible Future Energy Scenarios, concluded that 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 Security and Quality of Supply Standard (NETS SQSS).
To address this and meet its statutory duties, National Grid needs to reinforce the electricity network in East Anglia. The reinforcement is needed to allow power to be imported to, and exported from, East Anglia and to provide additional capability to allow power flows into and out of the south-east area to connect with areas of demand and interconnectors to Europe. This reinforcement is considered ‘critical’ in all Future Energy Scenarios.
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 and strengthening the existing network.
This can involve changing the conductors/wires on some of our existing overhead lines and adding smart power control devices to control the flow of electricity on parts of the network to transport it to where it is needed.
In East Anglia in the first half this decade, we are:
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
increasing the voltage of a section of line from Waltham Cross south into London to 400 kV to increase the capability of that part of the network into the capital
re-wiring existing overhead lines with conductors that can carry more power – for example on the existing overhead lines from Bramford to Braintree to Rayleigh to Tilbury, Twinstead and Pelham and between Norwich and Bramford.
Making these improvements will increase the capability of the existing network, but it is still insufficient to deliver the capability that National Grid ESO advises is required to deliver cleaner, greener energy to homes and businesses beyond the region in line with Government ambitions.
As National Grid ESO has outlined in the last two published NOAs, new reinforcements are needed in the region to deliver on the Government’s ambition to see 50 GW of offshore wind connected by 2030.