Electricity transmission and distribution networks ensure power is delivered from electricity generation facilities to your home. This section explores the transmission component of the electricity supply chain.
What is Electricity Transmission?
The electricity transmission network, also called the National Grid, transports electricity from generation facilities (power plants) to regional distribution areas.
Power stations generate electricity at around 22,000 volts. To lose as little energy as heat as possible when the electricity gets transported, substation transformers increase voltage to 270,000 and 400,000 volts before sending it into the National Grid electricity transmission network.
The National Grid’s high-voltage overground lines and underground cables are similar to a high-speed train network: electricity flows from one end of the United Kingdom to another to ensure supply meets demand at any time.
When electricity reaches a supply area (managed by a distribution network operator - DNO), substation transformers reduce electricity to 132,000 volts.
Electricity transmission networks in brief
Although there is a single electricity transmission system operator, the National Grid Electricity Transmission plc (NGET), the UK has four major electricity transmission networks, all privately owned.
Scottish Hydro Electric Transmission (SHE Transmission)
SHE transmission maintains and invests in the electricity transmission network in the north of Scotland. It is part of SSE (Scottish and Southern Energy), one of the UK’s largest energy companies that has operations in electricity generation, transmission, distribution and supply. SHE transmission’s network is 5,300km long and covers 70% of Scotland’s landmass.
SP Energy Networks
SP Energy Networks maintains and invests in the electricity transmission network in central and southern Scotland. It is also part of one of the Big Six energy companies: Scottish Power, with operations in electricity generation, transmission, distribution and supply. SP Energy Networks has over 4,000km of overhead cables and 320km of underground lines.
The National Grid
The National Grid maintains and invests in the electricity transmission network in England and Wales. It is an independent electricity transmission company that is also responsible for the overall supervision of electricity transmission in Great Britain (the system operator). Its power transmission operations in England and Wales cover 7,660km of high-voltage overhead cables and 1,400km of underground lines.
Northern Ireland Electricity (NIE)
Northern Ireland Electricity maintains and invests in the electricity transmission network in Northern Ireland. Unlike SHE Transmission, SP Energy Networks and the National Grid, it is connected to Ireland’s transmission network, not the UK’s. NIE is part of the ESB Group and covers over 2,000km of overhead and 80km of underground high-voltage cables.