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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. There are also undersea interconnections to northern France (HVDC Cross-Channel), Northern Ireland (HVDC Moyle), the Isle of Man (Isle of Man to England Interconnector), the Netherlands (BritNed) and the Republic of Ireland (EirGrid). On the breakup of the Central Electricity Generating Board in 1990, the ownership and operation of the National Grid in England and Wales passed to National Grid Company plc, later to become National Grid Transco, and now National Grid plc. In Scotland the grid split into two separate entities, one for southern and central Scotland and the other for northern Scotland, connected by interconnectors to each other. The first is owned and maintained by SP Energy Networks, a subsidiary of Scottish Power, and the other by SSE. However, National Grid plc remains the System Operator for the whole UK Grid. ==History== At the end of the 19th century, Nikola Tesla established the principles of three-phase high-voltage electrical power distribution while he was working for Westinghouse in the United States. The first to use this system in the United Kingdom was Charles Merz, of the Merz & McLellan consulting partnership, at his Neptune Bank Power Station near Newcastle upon Tyne. This opened in 1901, and by 1912 had developed into the largest integrated power system in Europe.〔(【引用サイトリンク】title=Survey of Belford 1995 )〕 The rest of the country, however, continued to use a patchwork of small supply networks. In 1925, the British government asked Lord Weir, a Glaswegian industrialist, to solve the problem of Britain's inefficient and fragmented electricity supply industry. Weir consulted Merz, and the result was the Electricity (Supply) Act 1926, which recommended that a "national gridiron" supply system be created.〔(【引用サイトリンク】title=Lighting by electricity )〕 The 1926 Act created the Central Electricity Board, which set up the UK's first synchronised, nationwide AC grid, running at 132 kV, 50 Hz. It began operating in 1933 as a series of regional grids with auxiliary interconnections for emergency use. Following the unauthorised but successful short term parallelling of all regional grids by the night-time engineers in 1937, by 1938 the grid was operating as a national system. The growth by then in the number of electricity users was the fastest in the world, rising from three quarters of a million in 1920 to nine million in 1938. It proved its worth during the Blitz when South Wales provided power to replace lost output from Battersea and Fulham power stations.〔 The grid was nationalised by the Electricity Act 1947, which also created the British Electricity Authority. In 1949, the British Electricity Authority decided to upgrade the grid by adding 275 kV links. The 275 kV Transmission System at the time of its inception in 1950, was designed to form part of a national supply system with an anticipated total demand of 30,000 MW by 1970. The predicted demand was already exceeded in 1960. The rapid load growth led to the Central Electricity Generating Board to carry out a study in 1960 of future transmission needs. The report was completed in September 1960, and its study is described in a paper presented to the Institution of Electrical Engineers by Messrs E.S. Booth, D. Clark, J.L. Egginton and J.S. Forrest in 1962. Considered in the study together with the increased demand was the effect on the transmission system of the rapid advances made in generation design field resulting in projected power stations of 2,000-3,000 MW’s installed capacity. These new stations were in the main to be sited where advantage could be taken of a surplus of cheap low-grade fuel and adequate supplies of cooling water, but these situations did not coincide with the load centres. West Burton with 4 x 500 MW machines, sited at the Nottinghamshire coalfield near the River Trent, is a typical example. These developments shifted the emphasis on the transmission system, from interconnection to the primary function of bulk power transfers from the generation areas to the load centres, such as the anticipated transfer in 1970 of some 6,000 MW from The Midlands to the Home counties. Continued reinforcement and extension of the existing 275 kV systems was examined as a possible solution. However, in addition to the technical problem of very high fault levels many more lines would have been required to obtain the estimated transfers at 275 kV. And as this was not consistent with the Central Electricity Generating Board's policy of preservation of amenities a further solution was sought. Consideration was given to a 400 kV and 500 kV as the alternatives, either of which gave a sufficient margin for future expansion. The decision in favour of a 400 kV system was made for two main reasons. Firstly the majority of the 275 kV lines could be uprated to 400 kV, and secondly it was envisaged that the operation at 400 kV could commence in 1965 compared with 1968 for a 500 kV scheme. Design work was started and in order to meet the programme for 1965 it was necessary for the contract engineering for the first projects to run con-currently with the design. One of these projects was the West Burton 400 kV Indoor Substation, the first section of which was commissioned in June 1965. From 1965, the grid was partly upgraded to 400 kV, beginning with a 150-mile (241 km) line from Sundon to West Burton, to become the ''Supergrid''. In the most recent issue of the code that governs the British Grid, the ''Grid Code'', the Supergrid is defined as referring to those parts of the British electricity transmission system that are connected at voltages in excess of 200 kV. British power system planners and operational staff therefore invariably speak of the Supergrid in this context; in practice the definition used captures all of the infrastructure owned by the National Grid company in England and Wales, and (in England and Wales) no other equipment. In 2013 the construction of the 2.2 GW undersea Western HVDC Link from Scotland to North Wales started, planned to be operational in 2016.〔(【引用サイトリンク】title=Q&A )〕 This is the first major non-alternating current grid link within the UK, though interconnects to foreign grids already use HVDC. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「National Grid (Great Britain)」の詳細全文を読む スポンサード リンク
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