Like much of the high voltage electricity transmission network across the country, the network between the North and the Midlands was largely built in the 1960s, carrying electricity down from Scotland and the North, connecting coal fired generation in the Aire and Trent valleys with the main centres of population.
The extent of the existing electricity transmission network in the region, the blue 400 kV lines and the red 275 kV lines, is shown on the map below and on our interactive map.
In the area north of the Humber, the network was initially developed to supply demand in and around Hull and the wider area. Two 400 kV overhead lines, each carrying two electrical circuits, connect Creyke Beck, near Cottingham, north of Hull. Creyke Beck and Salt End North are grid supply points where the local distribution network operator, Northern Powergrid, steps down the voltage to take electricity on, via their lower voltage distribution network, to homes and businesses.
In the late 1990s, gas fired generation at Salt End, east of Hull, was connected back to the transmission network at our Creyke Beck substation, via a new 275 kV overhead line from Salt End South substation. Creyke Beck and Hedon are also connection locations for existing offshore wind farms. In the Trent Valley, the electricity transmission network was built to connect major coal fired generation at Keadby, Cottam, Staythorpe, West Burton and High Marnham, carrying electricity on toward major population centres. Electricity still flows primarily from the North to the Midlands through the region today.
Why does the network in the region need reinforcing?
With growing offshore wind and interconnectors, an anticipated tripling of wind generation connected across the Scottish networks by 2030 and Government’s increased ambition to connect 50 GW of offshore wind by 2030, north-south power flows are set to increase. National Grid ESO in the Electricity Ten Year Statement anticipate that the network between the North and Midlands needs to transfer as much as 29 GW of electricity by 2033, compared to 11.6 GW that it can transfer today while remaining compliant with the standards the network is operated to.
The high voltage electricity transmission network in England and Wales operates largely at 400 kV and 275 kV. It connects separately owned generators, interconnectors, large demand users fed directly from the transmission system and the lower voltage distribution networks.
Most lines of pylons on the network carry two electrical circuits. 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.
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; and
the system remains electrically stable.
National Grid ESO oversees the standards, however, they are approved by a Security and Quality of Supply Standard panel and Ofgem.
Where power flows from one part of the network to another exceed the capability of the network across what we call ‘transmission boundaries’, one of two things need to happen.
Firstly, the System Operator might pay generators to reduce the energy they produce in one part of the country while paying others elsewhere to generate. These payments are called ‘constraint payments’. Balancing the network in this way can temporarily manage power flows where network capability is insufficient, but increases operation costs, as more expensive generation is brought on. This can be an economic way to manage the network up to a point, if constraint costs are not disproportionate. Where constraint costs are substantial, the network becomes uneconomic to operate. It then becomes necessary to invest in increasing network capability.
Transmission boundary B8 runs east to west, separating the northern generation zones including Scotland, Northern England and North Wales from the Midlands and southern demand centres. Across transmission boundary B8, the existing network can currently transport around 11.6 GW while remaining compliant with the standards the network is operated to.
Existing network capacity and demand in the Creyke Beck area
The existing network serving the Creyke Beck area can export just under 7 GW of electricity whilst remaining compliant with the Security and Quality of Supply Standards that the network is operated to. Whilst this has been sufficient until today, it is not sufficient to meet the power carrying capability that is required by the end of this decade and beyond.
Peak demand for electricity in the region in 2022 was 526.7 MW. Toward the end of the decade, electricity demand in the region is forecast to be higher than it is today, at around 585.7 MW in 2030 and 636.6 MW by 2032.
Future generation in the Creyke Beck area
As shown in the table below, there are a number of new sources of clean green energy contracted to connect in the Creyke Beck area in the next decade
With up to around 13 GW of contracted generation and interconnector capacity by the early 2030s, the network as it is today, notwithstanding local demand, would not have the capacity needed to export all that electricity out of the area across the B8 boundary. We therefore need to reinforce our network to prevent wider system failures and circuit overloads from happening.
When replacing the wires (conductors) on overhead lines, it is sometimes possible to do that with new ones that can carry more power and sometimes with wires that can be operated at a higher temperature allowing more power to be transported. That is what we are doing with the first two schemes. Power control devices are equipment that allow more power to be directed to flow along parts of the network that have some additional capacity.
While those works will increase the boundary transfer capability across boundary B8 to around 14 GW, they will not be sufficient to accommodate the north south power flows that are expected on the network. Up to around 29 GW of boundary transfer capability is needed by 2033 across the B8 boundary with increasing offshore wind and interconnectors.