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[[File:Nelson River Bipoles 1 and 2 Terminus at Rosser.jpg|thumb|right|300px|Long distance HVDC lines carrying [[hydroelectricity]] from Canada's [[Nelson River Hydroelectric Project|Nelson River]] to this [[HVDC Converter Station|converter station]] where it is converted to AC for use in southern [[Manitoba]]'s grid]]
A '''high-voltage, direct current''' ('''HVDC''') [[electric power transmission]] system (also called a '''power super highway''' or an '''electrical super highway''')<ref>{{cite web|url=http://www.abb.com/cawp/seitp202/40b621aafd3db79cc1257225002fcd3d.aspx|title=ABB opens era of power superhighways}}</ref><ref>{{cite web|url=http://www.windsystemsmag.com/article/detail/558/high-voltage-direct-current-hvdc-transmission-super-highway-benefits-to-the-plains-and-southeast|title=High Voltage Direct Current (HVDC) Transmission Super Highway Benefits to the Plains and Southeast}}</ref><ref>{{cite web|url=https://stateimpact.npr.org/oklahoma/2015/02/05/wind-power-superhighway-could-help-transform-panhandle-into-u-s-energy-hub/|title=Wind Power ‘Superhighway’ Could Help Transform Panhandle Into U.S. Energy Hub}}</ref><ref>{{cite web|url=https://books.google.es/books?id=XAQyZXvjusEC&pg=PA31&dq=High-voltage+direct+current+super+highway&hl=es&sa=X&ved=0CFMQ6AEwBWoVChMIs7bz8N3rxgIVTLIUCh3iUQnV#v=onepage&q=High-voltage%20direct%20current%20super%20highway&f=false|title=The Governance of Energy Megaprojects: Politics, Hubris and Energy Security}}</ref> uses [[direct current]] for the bulk transmission of electrical power, in contrast with the more common [[alternating current]] (AC) systems.<ref>Arrillaga, Jos; High Voltage Direct Current Transmission, second edition, Institution of Electrical Engineers, {{ISBN|0 85296 941 4}}, 1998.</ref>
HVDC allows power transmission between [[Synchronization (alternating current)|unsynchronized]] AC transmission systems. Since the power flow through an HVDC link can be controlled independently of the phase angle between source and load, it can stabilize a network against disturbances due to rapid changes in power. HVDC also allows transfer of power between grid systems running at different frequencies, such as 50 Hz and 60 Hz. This improves the stability and economy of each grid, by allowing exchange of power between incompatible networks.
The modern form of HVDC transmission uses technology developed extensively in the 1930s in [[Sweden]] ([[Allmänna Svenska Elektriska Aktiebolaget|ASEA]]) and in [[Germany]]. Early commercial installations included one in the [[Soviet Union]] in 1951 between [[Moscow]] and [[Kashira]], and a 100 kV, 20 MW system between [[Gotland]] and mainland Sweden in 1954.<ref>Narain G. Hingorani in ''[http://ieeexplore.ieee.org/iel3/6/10407/00486634.pdf?tp=&arnumber=486634&isnumber=10407 IEEE Spectrum]'' magazine, 1996. {{dead link|date=June 2016|bot=medic}}{{cbignore|bot=medic}}</ref>
[[Image:HVDC Europe.svg|thumb|right|350px|
{{legend|#F80E34|Existing links}}
{{legend|#10BF45|Under construction}}
{{legend|#0E25F8|Proposed}}
Many of these HVDC lines in 2008 transfer power from renewable sources such as hydro and wind. For names, see also the [[List of HVDC projects#Maps|annotated version.]]]]
==
== Advantages of HVDC over AC transmission ==
A
== Disadvantages ==
The disadvantages of HVDC are in conversion, switching, control, availability and maintenance.
HVDC is less reliable and has lower [[Availability factor|availability]] than alternating current (AC) systems, mainly due to the extra conversion equipment. Single-pole systems have availability of about 98.5%, with about a third of the downtime unscheduled due to faults. Fault-tolerant bipole systems provide high availability for 50% of the link capacity, but availability of the full capacity is about 97% to 98%.<ref>{{cite web|url=http://www.abb.com/industries/ap/db0003db004333/eb8b4075fb41252ec12574aa00409424.aspx |title=HVDC Classic reliability and availability |publisher=[[ABB Group|ABB]] |accessdate=2009-09-11 |deadurl=yes |archiveurl=https://web.archive.org/web/20140208095726/http://dnvgl.com/news-events/news/word-record-hvdc-transmission.aspx |archivedate=February 8, 2014 }}</ref>
The required [[HVDC converter station|converter stations]] are expensive and have limited overload capacity. At smaller transmission distances, the losses in the converter stations may be bigger than in an AC transmission line for the same distance.<ref>{{Cite web|url=http://www.lib.ncsu.edu/resolver/1840.16/10105|title=Design, Modeling and Control of Modular Multilevel Converter based HVDC Systems. - NCSU Digital Repository|website=www.lib.ncsu.edu|access-date=2016-04-17}}</ref> The cost of the converters may not be offset by reductions in line construction cost and lower line loss.
Operating a HVDC scheme requires many spare parts to be kept, often exclusively for one system, as HVDC systems are less standardized than AC systems and technology changes faster.
In contrast to AC systems, realizing multiterminal systems is complex (especially with line commutated converters), as is expanding existing schemes to multiterminal systems. Controlling power flow in a multiterminal DC system requires good communication between all the terminals; power flow must be actively regulated by the converter control system instead of relying on the inherent impedance and phase angle properties of an AC transmission line.<ref>{{cite book
| title = Standard Handbook for Electrical Engineers
| publisher = McGraw-Hill Professional
| date = August 25, 2006
| pages = 14–37 equation 14–56
| isbn = 978-0-07-144146-9
| author = Donald G. Fink and H. Wayne Beaty
}}</ref> Multi-terminal systems are rare. As of 2012 only two are in service: the [[Quebec – New England Transmission|Hydro Québec – New England transmission]] between Radisson, Sandy Pond and Nicolet<ref>{{cite web|url=http://www.abb.com/industries/ap/db0003db004333/87f88a41a0be97afc125774b003e6109.aspx |title=The HVDC Transmission Québec–New England |publisher=[[ABB Asea Brown Boveri]] |accessdate=2008-12-12 |deadurl=yes |archiveurl=https://web.archive.org/web/20110305134714/http://www.abb.com/industries/ap/db0003db004333/87f88a41a0be97afc125774b003e6109.aspx |archivedate=March 5, 2011 }}</ref> and the [[HVDC Italy–Corsica–Sardinia|Sardinia–mainland Italy]] link which was modified in 1989 to also provide power to the island of [[Corsica]].<ref>''The Corsican tapping: from design to commissioning tests of the third terminal of the Sardinia-Corsica-Italy HVDC''
Billon, V.C.; Taisne, J.P.; Arcidiacono, V.; Mazzoldi, F.;
Power Delivery, IEEE Transactions on
Volume 4, Issue 1, Jan. 1989 Page(s):794–799</ref>
==References==
{{Reflist|30em}}
==External links==
{{Commons category|HVDC}}
* [http://www.abb.com/hvdc ABB HVDC website]
* [http://www.alstom.com/grid/products-and-services/engineered-energy-solutions/hvdc-transmission-systems/ GE Grid Solutions HVDC website]
* [http://www.hvdc-plus.de/ HVDC PLUS from Siemens]
* [http://www.ptd.siemens.de/HVDC_Solutions_EPRI_Conference_09-07_V_1b.pdf UHVDC challenges explained from Siemens]
[[Category:High-voltage direct current| ]]
18:35, 25 April 2017 을 기반으로 번역
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