Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a transmission network. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is part of electricity delivery, known as the electrical grid.
A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems.
The Kontek HVDC is a 170-kilometre (110 mi) long, monopolar 400 kV high-voltage direct current cable between Germany and the Danish island Zealand. Its name comes from "continent" and the name of the former Danish power transmission company "Elkraft", which operated the power grid on the Danish islands Lolland, Falster and Zealand and had the abbreviation "ek". As of today, the cable is operated by Energinet.dk in Denmark and 50Hertz Transmission GmbH in Germany.
The Baltic Cable is a monopolar HVDC power line running beneath the Baltic Sea that interconnects the electric power grids of Germany and Sweden. Its maximum transmission power is 600 megawatts (MW).
The HVDC Inter-Island link is a 610 km (380 mi) long, 1200 MW high-voltage direct current (HVDC) transmission system connecting the electricity networks of the North Island and South Island of New Zealand together. It is commonly referred to as the Cook Strait cable in the media and in press releases, although the link is much longer than its Cook Strait section. The link is owned and operated by state-owned transmission company Transpower New Zealand.
HVDC Vancouver Island is a de-energized high-voltage direct current interconnection between Arnott Substation (ARN) in Delta, British Columbia at 49°5′31″N123°2′31″W on the Canadian mainland, and the Vancouver Island Terminal (VIT) in Duncan, British Columbia on Vancouver Island at 48°49′39″N123°42′55″W. It went into operation in 1968 and was extended in 1977. HVDC Vancouver Island consists of three overhead line sections with a total length of 42 kilometres and two submarine cable sections with a length of 33 kilometres. Pole 1 ceased operation in 2014, and Pole 2 ceased operation in 2016. The infrastructure remains in place and portions may be re-used in the future.
The Quebec – New England Transmission is a long-distance high-voltage direct current (HVDC) line between Radisson, Quebec and Westford Road in Ayer, Massachusetts. As of 2012, it remains one of only two Multi-terminal HVDC systems in the world and is "the only multi-terminal bipole HVDC system in the world where three stations are interconnected and operate under a common master control system".
Estlink is a set of HVDC submarine power cables between Estonia and Finland. Estlink 1 is the first interconnection between the Baltic and Nordic electricity markets followed by Estlink 2 in 2014. The main purpose of the Estlink connection is to secure power supply in both regions to integrate the Baltic and Nordic energy markets.
LitPol Link is an electricity link between Poland and Lithuania which connects the Baltic transmission system to the synchronous grid of Continental Europe. It has a capacity of 500 MW and since 2021 it can operate in a synchronous regime.
Hydro-Québec's electricity transmission system is an international electric power transmission system centred in Quebec, Canada. The system pioneered the use of very high voltage 735-kilovolt (kV) alternating current (AC) power lines that link the population centres of Montreal and Quebec City to distant hydroelectric power stations like the Daniel-Johnson Dam and the James Bay Project in northwestern Quebec and the Churchill Falls Generating Station in Labrador.
TenneT is a transmission system operator in the Netherlands and in a large part of Germany.
The Great Belt power link, also known as the Great Belt electricity link, is a high-voltage direct-current interconnection across the Great Belt between Funen and Zealand connecting two power transmission systems in Denmark.
The National Grid is the nationwide system of electric power transmission in New Zealand. The grid is owned, operated and maintained by Transpower New Zealand, a state-owned enterprise, although some lines are owned by local distribution companies and leased to Transpower. In total, the national grid contains 11,803 kilometres (7,334 mi) of high-voltage lines and 178 substations.
SydVästlänken is a project for reinforcement of power grids in Southern Sweden and Oslo area in Norway. The project to be implemented by Swedish and Norwegian national grids operators Svenska kraftnät and Statnett.
The Trans Bay Cable is a high-voltage direct current (HVDC) underwater transmission cable interconnection between San Francisco, California and Pittsburg, California. The 53 mi (85 km) cable under San Francisco Bay and through the Carquinez Strait can transmit 400 megawatts of power at a DC voltage of ±200 kV, enough to provide 40% of San Francisco's peak power needs.
The Talcher–Kolar HVDC system, otherwise known as the East–South interconnection II is a 1450 km HVDC transmission connection between the eastern and southern regions in India connecting four states namely Odisha, Andhra Pradesh, Tamil Nadu and Karnataka. The system has a transmission voltage of ±500 kV and was originally put into service in March 2003, with a rated power of 2000 MW. In 2007 the scheme was upgraded to 2500 MW.
The Xiangjiaba–Shanghai HVDC system is a ±800 kV, 6400 MW high-voltage direct current transmission system in China. The system was built to export hydro power from Xiangjiaba Dam in Sichuan province, to the major city of Shanghai. Built and owned by State Grid Corporation of China (SGCC), the system became the world’s largest-capacity HVDC system when it was completed in July 2010, although it has already been overtaken by the 7200 MW Jinping–Sunan HVDC scheme which was put into operation in December 2012. It also narrowly missed becoming the world’s first 800 kV HVDC line, with the first pole of the Yunnan–Guangdong project having been put into service 6 months earlier. It was also the world’s longest HVDC line when completed, although that record is also expected to be overtaken early in 2013 with the completion of the first bipole of the Rio Madeira project in Brazil.
ElecLink is a 1,000 MW high-voltage direct current (HVDC) electrical interconnector between the United Kingdom and France, passing through the Channel Tunnel. ElecLink commenced operations on 25 May 2022.
The Matambo–Phombeya High Voltage Power Line is a high voltage electricity power line under construction, connecting the high voltage substation at Matambo, Tete Province, Mozambique to another high voltage substation at Phombeya, Balaka District, Malawi.
