Entry points include power stations, major wind farms and inter-connectors from other countries and regions.
The substations and the grid operated at 132 kV and provided local and regional inter-connections.
[3] The first 400 kV substations in Scotland were commissioned in 1972 associated with the line from Hunterston, Ayrshire to Neilston, Renfrewshire.
[2] The appearance of substations, and their visual impact, was improved using earth mounds and trees.
[2] In 1972 a Mark II low profile 400 kV substation was commissioned, the first was at Wymondley, Hertfordshire.
[3] The rapid development of the 400 kV system is demonstrated in the numbers of new substations that were being built: in 1971 ten 400 kV substations were commissioned by the CEGB, these were: Pheasant Farm, Abham, Didcot, Exeter, Hinkley Point, Indian Queens, Landulph, Melksham, Drax and Harker.
It also operates the grid and substations in Scotland although the systems are owned by ScottishPower and Scottish & Southern Energy.
In addition the 600 kV DC Western HVDC underground and sub-marine link connects Flintshire Bridge Converter station, in Flintshire Wales, to the Western HVDC Converter station near Hunterston.
[8][10][11][12][13] The Moyle Interconnector provides a high-voltage link between the Scotland and Northern Ireland 275 kV systems.