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The National Grid is the nationwide system of electric power transmission in New Zealand. The national electricity transmission grid is owned, operated, and maintained by state-owned enterprise Transpower New Zealand. In total, the national grid contains of high-voltage lines and 178 substations. Much of New Zealand’s electricity generation is hydro-electric. The majority of this generation is from stations established on lakes and rivers in the lower half of the South Island, while most of the electricity demand is in the North Island, in particular, the Auckland region. Consequently, large amounts of electricity need to be transmitted long distances over the grid, between generation and load, including transmission across Cook Strait, between the two islands, via the HVDC link. 〔(【引用サイトリンク】title= A Guide to Transpower 2009 )〕 Investments in new transmission are regulated by the Commerce Commission. In a news release in January 2012, the Commerce Commission reported that Transpower was planning to invest $5 billion over the next 10 years in upgrades of critical infrastructure. ==History== Initial use of electricity in New Zealand was associated with mining. The first industrial hydro-electric power plant was established at Bullendale in Otago in 1885, to provide power for a 20 stamp battery at the Phoenix mine. The plant used water from the nearby Skippers Creek, a tributary of the Shotover River.〔(【引用サイトリンク】title= Phoenix Mine Hydro Electric Plant Site, New Zealand Historic Places Trust )〕 There was a two mile long transmission line from the generating station to the stamping battery.〔Reilly, H (2008) p. 17-18〕 The first transmission line constructed by the government was associated with the Okere Falls Power Station near Rotorua. Electricity was transmitted at 3.3 kV over a 13-mile route to Rotorua, and was used to drive sewage pumps, and some public buildings including five thermal baths.〔Martin, J (1998) p. 38-40〕 The first major transmission line in the North Island was constructed in 1913-14, connecting the Horahora hydro station to Waikino to meet the power requirements of the stamp battery 5 miles further on at the Waihi gold mine. The line length between Horahora and Waikino was 45 miles, and the transmission voltage was 50 kV, which was to set a precedent for North Island transmission voltage for many years.〔Reilly, H (2008) p. 45-52〕 The first major transmission line in the South Island was constructed by the government as part of the Coleridge hydro station development, and was commissioned in 1914. Two transmission lines operating at 66 kV carried the power from Coleridge over a distance of 65 miles to Addington in Christchurch.〔Martin, J (1998) p. 51〕 Following World War I, regional networks began to develop using 110 kV transmission lines to connect towns and cities with remote hydroelectric schemes. By 1930, there were three major transmission networks: the Arapuni system stretched from the Hibiscus Coast in the north to Otorohanga and Rotorua in the south and Opotiki in the east; the Mangahao-Waikaremoana system stretched from Wellington north to Gisborne and west to Wanganui; and the Coleridge system stretched along coastal Canterbury from Rangiora to Oamaru. During the Depression years, the Arapuni and Mangahao-Waikaremoana systems were connected via Taranaki and the system extended north to Whangarei. The Coleridge system extended south to link with Dunedin's Waipori system and Southland's Monowai system, inland from Oamaru to the Waitaki dam, and west over Arthur's Pass to Greymouth. The State Hydro-electric Department was established in 1946 to oversee the development of electricity generation and transmission to meet rapidly growing demand. Nelson and Marlborough were the last regions to join the national grid system when a transmission line between Inangahua and Stoke was completed in 1955. The construction of the 220 kV network began in the early 1950s, initially connecting Auckland to Wellington, and Christchurch to Roxburgh. The first North Island 220 kV line was commissioned between Maraetai and Whakamaru in October 1952, and the first South Island 220 kV line was commissioned between Roxburgh and Islington in July 1956.〔Reilly, H (2008) p. 124-129〕 In 1958 the State Hydro-electric Department was changed into the NZ Electricity Department (NZED), reflecting the development of thermal generation to supplement the hydro-electric schemes. The electricity systems of the two islands were joined together by the HVDC Inter-Island link in 1965, connecting Benmore in the South Island with Haywards in the North Island. The original link used mercury arc valve converters, and was rated at . It was the first HVDC link to be commissioned in the Southern Hemisphere. In 1978, the Electricity Division of the Ministry of Energy was established to integrate the state-owned electricity generation and transmission business with the oil, gas and coal businesses of the government owned energy sector. In 1987, the Electricity Corporation of New Zealand (ECNZ) was established as a State Owned Enterprise, and in 1988, the transmission business was established as a subsidiary within ECNZ, taking the name Transpower New Zealand.〔Reilly, H (2008) p. 329〕 The late 1980s and early 1990s saw the completion of the 220 kV backbone, with the last line connecting Stratford in Taranaki to Huntly in Waikato. The HVDC Inter-Island was also upgraded by increasing the operating voltage of the lines, replacing the original Cook Strait submarine cables and installing a new thyristor pole in parallel to the existing mercury arc valve converter equipment to double its capacity to 1240 MW. In 1994, Transpower was separated from Electricity Corporation of New Zealand to become a State Owned Enterprise in its own right. 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 (New Zealand)」の詳細全文を読む スポンサード リンク
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