In the next decade Great Britain’s electricity network requires major expansion to meet Net Zero investments, according to the system operator’s regular ‘Electricity Ten Year Statement’ (ETYS), which considers where investment or reinforcement is needed to ensure the grid remains fit for purpose.
The ETYS considers the network capability by looking at whether the power transferred between two regions (‘across a boundary’) exceeds the capacity available at the boundary. If there is more power than can be transferred, the network operator has to ‘constrain’ generators – pay them to switch off – unless a local user for their power can be found.
It says reinforcements are needed within the decade or the system “would be significantly constrained due to high flows from the increased generation capacity”. And it is a moving target: “Due to the growth in government ambition … our boundary flow requirements are higher than last year.”
The investment is needed first to accommodate changes in power flows across the country, system operator NGESO said. It anticipates a tripling of wind generation connected across Scottish networks by 2030, driving higher north-to-south power transfers. As gross demand in Scotland is not expected to exceed 6GW by 2030 – already less than the Scottish generation capacity – and both offshore wind farms and other generation is in development, Scotland will be expected to export power into England most of the time, but power flows could vary widely because at times of low wind power may flow the other way.
The sysetm operator also said that transfer requirements from northern Scotland and northern England to the Midlands would double over the next 10 years, so “new reinforcements will be required to facilitate these power flows through the North of England”. This is a major shoft from past decades, when there was extensive coal and gas fired generation near users in northern England and the Midlands. NGESO said “Electricity demand is predominantly located in the south, leading to high north-south power flows. These flows are highly variable due to the intermittent nature of wind generation and interconnection. The system will need to be prepared to manage large swings in power flows. The highly variable nature of power flows in the north presents challenges for voltage management.The north-south flows contribute significantly to system constraints across the entire GB transmission system.”
Gross demand in the North of England in expected to increase to a total of up to 11GW by 2030, but generation in the region is already double that figure, and will increase by an additional 5GW by 2020. The North of England is a heavily power-exporting region and must also manage power flows from Scotland to the demand centres in the Midlands and South.
Secondly the statement highlighted power from offshore wind, as it noted that the Ten Point Plan published by the government included increased ambition for offshore wind – now set to reach 40 GW of installed capacity by 2030. As well as power transported from Scotland, that would mean offshore wind connecting along the east coast – as well as up to 12GW increase in transmission-connected low-carbon and renewable generation onshore in the region. It said “The total generation in all the scenarios will exceed the local demand; thus the East of England will be a power exporting region.” But again that will vary when the wind is low.

Interconnectors
The statement also highlighted new interconnectors – and this week Ofgem announced that it would open a new application window for interconnectors with the aim of increasing interconnector capacity to 18GW by 2030. New interconnectors in the eastern region are expected to increase the transfer requirements, including during low-wind periods. But they will also place increased requirements on the transmission network around London and South East England and likely exceed the region’s current capacity. BGESO says, “In the future, the southern network could potentially see a number of issues driven by future connections. If the interconnectors export power to Europe at the same time that high demand power is drawn both into and through London, then the northern circuits feeding London will be thermally overloaded.”
Finally the ETYS notes that less ‘synchronous generation’ – traditional plant with heavy rotating machinery that gives the grid supply stability – could lead to challenges with reduced short circuit levels and inertia. It is already seeking alternative ways to provide these services. In London and the South East, for example, NGESO says high demand and power flows may lead to voltage depression. It says, “The closure of conventional generation within the region will present added stability and voltage depression concerns which may need to be solved through reinforcements.”
Download the Electricity Ten Year Statement here