The National Grid is the high-voltage electric power transmission network in Great Britain, connecting power stations and major substations and ensuring that electricity generated anywhere in England, Scotland and Wales can be used to satisfy demand elsewhere.
Formation of the Grid
1925 The Government appointed a Committee chaired by Lord Weir to review the national problem of the supply of electrical energy and report on the most efficient and effective development of the supply of electricity. The main recommendations of the Committee were: that a national system of main transmission lines, designated the "Grid," should be established for the purpose of interconnecting the systems of all the public supply authorities in the country and enabling them to be supplied, on a wholesale basis, with electricity produced at the most efficient stations; that an executive body - the Central Electricity Board — which should be responsible for the erection and operation of the "Grid" and should direct the operations of the station "selected" to feed it; that the frequency of the alternating current systems in the country should be standardized. These recommendations were adopted by Parliament and given effect to by the Electricity (Supply) Act of 1926
1927 The Central Electricity Board was established as a statutory body (but not a Government department). Its main purpose was to organize the construction of the "Grid" - to this end, the country was divided into ten main areas, namely: North Scotland, Central Scotland, South Scotland, North- East England, North-West England and North Wales, Mid-East England, Central England, East England, South-East England, and South-West England and South Wales. For each of these areas, except North Scotland, regional schemes were designed so that they would dovetail with each other.
1928 Construction began in Central Scotland early in 1928, and the last tower for the main transmission system was erected on the outskirts of the New Forest at the beginning of September, 1933. In total there were 4,000 miles of transmission lines, including 2,894 miles of primary lines operating at 132 kvolts, and 1,106 miles of secondary lines operating at lower voltages. The primary lines included 15 route miles of cable and the secondary lines, 102 route miles of cable laid within the London area. In the system there were 26,265 towers, averaging 75 feet in height and over three tons in weight.
Approximately 60 rivers had to be crossed, involving the construction of special towers of varying height. The largest towers in the Grid were those for the Thames crossing at Dagenham. They were 487 feet high and weighed 290 tons each. The span of the conductors between the towers was 3,060 feet. Other tall towers were for crossing the Forth at Kincardine, the River Roding at Barking Creek, the Severn crossing at Upper Arlingham, and the Clyde crossing at Yoker.
Of the 438 power stations identified in the Weir Committee report, only 140 larger, central stations supplied the grid. Many smaller, isolated, stations were closed down, although some establishments bought from, and sold surpluses to the grid, whilst others continued to generate electricity for their own use in factories, hospitals and country estates.
1940 the Electricity Commissioners, in agreement with the Central Electricity Board, proposed a programme of new generating capacity to mitigate war risks and the growth in demand associated with the development of munitions factories. The programme entailed the installation of 180 MW of plant in four existing stations and two new stations one at Earley, east of Reading, and the other at Castle Meads, Gloucester.
1948 The successor organisation to the CEB was the British Electricity Authority. The BEA was given responsibility for generation and transmission whilst the Area Boards had responsibility for the distribution and sale of electricity to consumers. It was decided that the existing 132kV grid was insufficient and plans were put in place to build a grid operating at 275kV with potential to uprate to 400kV.
1955 The BEA was replaced by the Central Electricity Authority in England and Wales
1958 The CEA was replaced by the Central Electricity Generating Board.
The CEGB had a duty to develop and maintain an efficient, co-ordinated and economical system of supply of electricity in bulk for all parts of England and Wales, and for that purpose to generate or acquire supplies of electricity and to provide bulk supplies of electricity for the Area Boards for distribution by those Boards. It also had power to supply bulk electricity to the Scottish Boards or electricity undertakings outside Great Britain.
At the centre was the National Control Room of the National Grid in London, which was part of the control hierarchy for the system. There were also both area and district grid control rooms, which were originally at Newcastle upon Tyne, Leeds, Manchester, Nottingham, Birmingham, St Albans, East Grinstead and Bristol. The shift control engineers who worked in these control rooms would cost, schedule and load dispatch an economic commitment of generation to the main interconnected system at an adequate level of security. They also had information about the running costs and availability of every power producing plant in England and Wales. They constantly anticipated demand, monitored and instructed power stations to increase, reduce or stop electricity production. They used what was known as the "merit order", a ranking of each generator in power stations based upon how much they cost to produce electricity. The objective was to ensure that electricity production was achieved at the lowest possible cost.
At the time the CEGB came into existence, half of the planned upgrade to 275kV had been implemented with the remaining 900 miles of line under construction. Nevertheless, the need for upgrading to 400kV was becoming apparent, not least to serve the new "super power stations" then being planned.
1961 A Transmission Construction Project was formed to build the 400kV supergrid.
By 1965 the first 150 mile length of new 400kV line had been completed (as well as uprating some lengths of 275kV lines).
c1970 About 1300 miles of 400kV line were in operation. This was followed by uprating about 1500 miles of 275kV lines.
The 2000MW undersea link with France was brought into operation in the 1970s.
1990 On the breakup of the CEGB, the ownership and operation of the National Grid in England and Wales passed to National Grid Company plc.
In Scotland the grid was split into two separate entities, one for southern and central Scotland and the other for northern Scotland, connected by inter-connectors. The first is owned and maintained by SP Energy Networks, a subsidiary of Scottish Power, and the northern part by SSE. However, National Grid plc remains the System Operator for the whole UK Grid.
2000 Lattice Group plc was formed from BG Group plc, responsible for UK Gas Transmission and Distribution (which by then has been reshaped into eight networks, from the 12 Regions) and including ownership of Transco. Lattice also owned a number of telecoms infrastructure businesses including SST (UK) Ltd. Other businesses held under the Lattice Enterprises portfolio included Advantica, Fulcrum Connections, Lattice Energy Services and Lattice Property.
2002 Lattice Group plc and National Grid Group plc merged to form a new company – National Grid Transco plc
2005 The name of National Grid Transco plc was changed to National Grid plc.
This merger united the UK gas and high voltage electricity transmission businesses, the UK Gas distribution business and other subsidiaries including US Gas & Electricity Distribution business. During 2005, four of the eight gas distribution networks were sold to private buyers.
In October 2016 the remaining four National Grid Gas Distribution Networks became an independent company. Cadent is the new name and is an independent company in its own right, owned by a consortium of investors.