A high-voltage, direct current (HVDC) electric power transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be justified, due to other benefits of direct current links. HVDC uses voltages between 100 kV and 1,500 kV.
The Baltic Cable is a monopolar HVDC power line running beneath the Baltic Sea that interconnects the electric power grids of Germany and Sweden.
The HVDC Volgograd–Donbass is a 475 kilometres (295 mi) long bipolar ±400 kV high voltage direct current powerline used for transmitting electric power from Volga Hydroelectric Station at Volgograd in Russia to Donbass in eastern Ukraine and vice versa.
The HVDC Cross-Channel is the name given to two different high voltage direct current (HVDC) interconnectors that operate or have operated under the English Channel between the continental European and British electricity grids.
The Pacific DC Intertie is an electric power transmission line that transmits electricity from the Pacific Northwest to the Los Angeles area using high voltage direct current (HVDC). The line capacity is 3,100 megawatts, which is enough to serve two to three million Los Angeles households and represents almost half (48.7%) of the Los Angeles Department of Water and Power (LADWP) electrical system's peak capacity.
The GK Vienna–Southeast was a back-to-back HVDC station linking the electric power grids of Austria and Hungary. It operated between June 1993 and October 1996.
An HVDC converter station is a specialised type of substation which forms the terminal equipment for a high-voltage direct current (HVDC) transmission line. It converts direct current to alternating current or the reverse. In addition to the converter, the station usually contains:
The HVDC Itaipu is a High-voltage direct current overhead line transmission system in Brazil from the Itaipu hydroelectric power plant to the region of São Paulo. The project consists of two ±600 kV bipoles, each with a rated power of 3150 MW, which transmit power generated at 50 Hz from the Paraguay side of the Itaipu Dam to the Ibiúna converter station near São Roque, São Paulo. The system was put in service in several steps between 1984 and 1987, and remains among the most important HVDC installations in the world.
The IPP DC Line is a bipolar HVDC transmission line between Adelanto Converter Station 34°33′4″N117°26′14″W in Adelanto, California and Intermountain Converter Station 39°30′2″N112°34′51″W near Delta, Utah.
Shin-Shinano Frequency Converter is the designation of a back-to-back high-voltage direct current (HVDC) facility in Japan which forms one of four frequency converter stations that link Japan's western and eastern power grids. The other three stations are at Higashi-Shimizu, Minami-Fukumitsu and Sakuma Dam.
The HVDC Sileru–Barsoor is a high voltage direct current transmission system between Sileru and Barsoor in India. It is in service since 1989 as the first HVDC line in the country. The HVDC Sileru–Barsoor is a bipolar HVDC with a voltage of 200 kV and a transmission rate of 400 megawatts. The HVDC Sileru–Barsoor couples two asynchronously operated parts of Indian electricity mains over a 196 kilometres (122 mi) long overhead line, which was originally a double-circuit 220 kV AC line from which three conductors are paralleled.
GKK Etzenricht, abbreviation for Gleichstromkurzkupplung Etzenricht, that means Etzenricht HVDC-back-to-back station, was an HVDC back-to-back facility near Etzenricht in the district of Neustadt an der Waldnaab in Bavaria, Germany. It was built up on area of Etzenricht substation, a 380 kV/220 kV/110 kV-substation, which went in service in 1970 and expanded afterwards several times. The operator of this facility, which was used between 1993 and 1995 for exchange of power between Germany and Czech, was Bayernwerk AG.
The Vyborg HVDC scheme is a system of electricity transmission from the Russian power system to Finland, using high-voltage direct current. It consists of four, 355 MVA (250 MW) back-to-back converter blocks, the first three of which were completed in the early 1980s and the last in January 2001. Much of the original converter equipment has been refurbished or modernised.
Amtrak's 25 Hz traction power system is a traction power grid operated by Amtrak along the southern portion of its Northeast Corridor (NEC): the 225 route miles (362 km) between Washington, D.C. and New York City and the 104 route miles (167 km) between Philadelphia and Harrisburg, Pennsylvania. The Pennsylvania Railroad constructed it between 1915 and 1938. Amtrak inherited the system from Penn Central, the successor to Pennsylvania Railroad, in 1976 along with the Northeast Corridor. This is the reason for using 25 Hz, as opposed to 60 Hz – which is the standard for power transmission in North America. In addition to serving the NEC, the system provides power to New Jersey Transit Rail Operations (NJT), the Southeastern Pennsylvania Transportation Authority (SEPTA) and the Maryland Area Regional Commuter Train (MARC). Only about half of the system's electrical capacity is used by Amtrak. The remainder is sold to the commuter railroads who operate their trains along the corridor.
The Black Sea Transmission Network is a project for electric power transmission from Georgia to Turkey.
Rivera HVDC Back-to-back station is the first HVDC Back-to-back station situated south of Rivera, Uruguay at 30°56′29″S55°33′34″W. It was built by Areva and inaugurated in 2000. Rivera HVDC Back-to-back station whose function is to perform a conversion of 50 Hz power from the power grid of Uruguay into 60 Hz for the power grid of Brazil, operates with a DC voltage of 20 kV. The transmission rate is 70 MW. Rivera HVDC Back-to-back station is connected with the power grid of Uruguay by a short single-circuit 150 kV line to Rivera substation situated at 30°56′39″S55°33′9″W. The connection to the power grid of Brazil is done by a single-circuit 230 kV AC line, which crosses the border between Uruguay and Brazil at 30°52′17″S55°33′30″W and ends at Livramento Substation 30°51′44″S55°32′34″W. As this interconnection does not fit today's requirement, a second interconnection over Melo HVDC Back-to-back station was built.
The Al-Fadhili back-to-back HVDC station is a back-to-back HVDC connection between Saudi Arabia, whose grid operates at 60 Hz, and its neighbouring Gulf states which have 50 Hz grids. The station is located in Saudi Arabia, approximately 100 km north-west of Dammam, but was built for and owned by Gulf Cooperation Council Interconnection Authority (GCCIA). The converter station was built by Areva T&D, now Alstom Grid, between 2006 and 2009.
The Rio Madeira HVDC system is a high-voltage direct current transmission system in Brazil, built to export power from new hydro power plants on the Madeira River in the Amazon Basin to the major load centres of southeastern Brazil. The system consists of two converter stations at Porto Velho in the state of Rondônia and Araraquara in São Paulo state, interconnected by two bipolar ±600 kV DC transmission lines with a capacity of 3,150 megawatts (4,220,000 hp) each. In addition to the converters for the two bipoles, the Porto Velho converter station also includes two 400 MW back-to-back converters to supply power to the local 230 kV AC system. Hence the total export capacity of the Porto Velho station is 7100 MW: 6300 MW from the two bipoles and 800 MW from the two back-to-back converters. When Bipole 1 commenced commercial operation in 2014, Rio Madeira became the world’s longest HVDC line, surpassing the Xiangjiaba–Shanghai system in China. According to the energy research organisation Empresa de Pesquisa Energética (EPE), the length of the line is 2,375 kilometres (1,476 mi).
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.
Adelanto Converter Station in Adelanto, California is the southern terminus of the 2,400 MW Path 27 Utah–California high voltage DC power (HVDC) transmission line. The station contains redundant thyristor-based HVDC converters rated for 1,200 MW continuous or 1,600 MW short term overload. The 300-acre (120 ha) station was completed in July, 1986 at a cost of US$131 million. The northern terminus of Path 27 is fossil fueled Intermountain Power Plant in Utah.
