Submarine power cable

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Cross section of the submarine power cable used in Wolfe Island Wind Farm.

A submarine power cable is a major transmission cable for carrying electric power below the surface of the water.[1] These are called "submarine" because they usually carry electric power beneath salt water (arms of the ocean, seas, straits, etc.) but it is also possible to use submarine power cables beneath fresh water (large lakes and rivers). Examples of the latter exist that connect the mainland with large islands in the St. Lawrence River.

Design technologies[edit]

The purpose of submarine power cables is the transport of electric current at high voltage. The electric core is a concentric assembly of inner conductor, electric insulation and protective layers.[2] Modern three-core cables (e.g. for the connection of offshore wind turbines) often carry optical fibers for data transmission or temperature measurement, in addition to the electrical conductors.

Conductor[edit]

The conductor is made from copper or aluminum wires, the latter material having a small but increasing market share. Conductor sizes ≤ 1200 are most common, but sizes ≥ 2400 mm2 have been made occasionally. For voltages ≥ 12 kV the conductors are round. The conductor can be stranded from individual round wires, or can be a single solid wire. In some designs, profiled wires (keystone wires) are laid up to form a round conductor with very small interstices between the wires.

Insulation[edit]

Three different types of electric insulation around the conductor are mainly used today. Cross-linked polyethylene (XLPE) is used up to 420 kV system voltage. It is produced by extrusion in insulation thickness of up to about 30 mm. 36 kV class cables have only 5.5 – 8 mm insulation thickness. Certain formulations of XLPE insulation can also be used for DC. Low-pressure oil-filled cables have an insulation lapped from paper strips. The entire cable core is impregnated with a low-viscosity insulation fluid (mineral oil or synthetic). A central oil channel in the conductor facilitates oil flow when the cable gets warm. Rarely used in submarine cables due to oil pollution risk at cable damage. Is used up to 525 kV. Mass-impregnated cables have also a paper-lapped insulation but the impregnation compound is highly viscous and does not exit when the cable is damaged. MI insulation can be used for massive HVDC cables up to 525 kV.

Armoring[edit]

Cables ≥ 52 kV are equipped with an extruded lead sheath to prevent water intrusion. No other materials have been accepted so far. The lead alloy is extruded onto the insulation in long lengths (over 50 km is possible). In this stage the product is called cable core. In single-core cables the core is surrounded by a concentric armoring. In three-core cables, three cable cores are laid-up in a spiral configuration before the armoring is applied. The armoring consists most often of steel wires, soaked in bitumen for corrosion protection. Since the alternating magnetic field in ac cables causes losses in the armoring those cables are sometimes equipped with non-magnetic metallic materials (stainless steel, copper, brass).

AC or DC[edit]

Most electrical power transmission systems use alternating current (AC), because transformers can easily change voltages as needed. Direct-current transmission requires a converter at each end of a direct current line to interface to an alternating current grid. A system using submarine power cables may be less costly overall if using high-voltage direct current transmission, especially on a long link where the capacitance of the cable would require too much additional charging current. The inner and outer conductors of a cable form the plates of a capacitor, and if the cable is long (on the order of tens of kilometres), the current that flows through this capacitance may be significant compared to the load current. This would require larger, therefore more costly, conductors for a given quantity of usable power to be transmitted.

Operational submarine power cables[edit]

Alternating current cables[edit]

Alternating-current (AC) submarine cable systems for transmitting lower amounts of three-phase electric power can be constructed with three-core cables in which all three insulated conductors are placed into a single underwater cable. Most offshore-to-shore wind-farm cables are constructed this way.

For larger amounts of transmitted power, the AC systems are composed of three separate single-core underwater cables, each containing just one insulated conductor and carrying one phase of the three phase electric current. A fourth identical cable is often added in parallel with the other three, simply as a spare in case one of the three primary cables is damaged and needs to be replaced. This damage can happen, for example, from a ship's anchor carelessly dropped onto it. The fourth cable can substitute for any one of the other three, given the proper electrical switching system.

Connecting Connecting Voltage (kV) Notes
Mainland British Columbia to Texada Island to Nile Creek Terminal Vancouver Island / Dunsmuir Substation 525 Reactor station at overhead crossing of Texada Island. Two three-phase circuits using twelve, separate, oil filled single-phase cables. Shore section cooling facilities. Nominal rating 1200 MW (1600 MW - 2hr overload)
Tarifa, Spain
(Spain-Morocco Interconnection)
Fardioua, Morocco
through the Strait of Gibraltar
400 The Spain-Morocco Interconnection consists of two 400-kV, AC submarine cables operated jointly by Red Eléctrica de España (Spain) and Office National de l'Électricité (Morocco); the first, 28-kilometre (17 mi) cable, began operating in 1998, the second, of length 31 kilometres (19 mi) began operation in 2006 .[3] The total underwater length of the cables through the Strait of Gibraltar is 26 kilometres (16 mi) and the maximum depth is 660 metres (2,170 ft).[4]
Mainland Sweden Bornholm Island, Denmark 60 The Bornholm Cable
Mainland Italy Sicily 380 Under the Strait of Messina, this submarine cable replaced an earlier, and very long overhead line crossing (the "Pylons of Messina")
Germany Heligoland 30 [5]
Negros Island Panay Island, the Philippines 138
Douglas Head, Isle of Man, Bispham, Blackpool, England 90 The Isle of Man to England Interconnector, a 3 core cable over a distance of 104 kilometres (65 mi)
Wolfe Island, Canada Kingston, Canada 245 The 7.8 kilometres (4.8 mi) cable installed in 2008 for the Wolfe Island Wind Farm was the world's first three-core XLPE submarine cable to achieve a 245 kV voltage rating.[6]

Direct current cables[edit]

Name Connecting Body of water Connecting kilovolts (kV) Undersea distance Notes
Baltic Cable Germany Baltic Sea Sweden 450 250 kilometres (160 mi)
Basslink mainland State of Victoria Bass Strait island State of Tasmania, Australia 500 290 kilometres (180 mi)[7]
BritNed Netherlands North Sea Great Britain 450 260 kilometres (160 mi)
Cross Sound Cable Long Island, New York Long Island Sound State of Connecticut [citation needed]
East–West Interconnector Ireland Irish Sea Wales/England and thus the British grid 186 kilometres (116 mi) Inaugurated 20 September 2012
Estlink northern Estonia Gulf of Finland southern Finland 330 105 kilometres (65 mi)
Fenno-Skan Sweden Baltic Sea Finland 400 233 kilometres (145 mi)
HVDC Cross-Channel French mainland English Channel England very high power cable (2000 MW)[citation needed]
HVDC Gotland Swedish mainland Baltic Sea Swedish island of Gotland the first HVDC submarine power cable (non-experimental)[citation needed]
HVDC Inter-Island South Island Cook Strait North Island 40 kilometres (25 mi) between the power-rich South Island (much hydroelectric power) of New Zealand and the more-populous North Island
HVDC Italy-Corsica-Sardinia (SACOI) Italian mainland Mediterranean Sea the Italian island of Sardinia, and its neighboring French island of Corsica[citation needed]
HVDC Italy-Greece Italian mainland - Galatina HVDC Static Inverter Adriatic Sea Greek mainland - Arachthos HVDC Static Inverter 400 160 kilometers (100 miles) Total length of the line is 313 km (194 mi)
HVDC Leyte - Luzon Leyte Island Pacific Ocean Luzon in the Philippines[citation needed]
HVDC Moyle Scotland Irish Sea Northern Ireland within the United Kingdom, and thence to the Republic of Ireland
HVDC Vancouver Island Vancouver Island Strait of Georgia mainland of the Province of British Columbia
Kii Channel HVDC system Honshu Kii Channel Shikoku 250 50 kilometres (31 mi) in 2010 the world's highest-capacity[citation needed] long-distance submarine power cable[inconsistent] (rated at 1400 megawatts). This power cable connects two large islands in the Japanese Home Islands
Kontek Germany Baltic Sea Denmark
Konti-Skan[8] Sweden Baltic Sea Denmark 400 149 kilometres (93 mi)
Neptune Cable State of New Jersey Atlantic Ocean Long Island, New York 345 103 kilometres (64 mi)[9]
NordBalt Sweden Baltic Sea Lithuania 300 400 kilometres (250 mi) Operations started on February 1, 2016 with an initial power transmission at 30 MW.[10]
Skagerrak 1-4 Norway Skagerrak Denmark (Jutland) 500 240 kilometres (150 mi) 4 cables - 1700 MW in all[11]
SwePol Poland Baltic Sea Sweden 450
NorNed Eemshaven, Netherlands Feda, Norway 450 580 kilometres (360 mi) 700 MW in 2012 the longest undersea power cable[12]

Submarine power cables under construction[edit]

Proposed submarine power cables[edit]

See also[edit]

References[edit]

  1. ^ a b c Underwater Cable an Alternative to Electrical Towers, Matthew L. Wald, New York Times, 2010-03-16, accessed 2010-03-18.
  2. ^ "Submarine Power Cables - Design, Installation, Repair, Environmental aspects", by T Worzyk, Springer, Berlin Heidelberg 2009
  3. ^ "A Bridge Between Two Continents", Ramón Granadino and Fatima Mansouri, Transmission & Distribution World, May 1, 2007. Consulted March 28, 2014.
  4. ^ "Energy Infrastructures in the Mediterranean: Fine Accomplishments but No Global Vision", Abdelnour Keramane, IEMed Yearbook 2014 (European Institute of the Mediterranean), under publication. Consulted 28 March 2014.
  5. ^ "Mit der Zukunft Geschichte schreiben". Dithmarscher Kreiszeitung (in German). Archived from the original on 2011-07-19. 
  6. ^ "Wolfe Island Wind Project" (PDF). Canadian Copper CCBDA (156). 2008. Retrieved 3 September 2013. 
  7. ^ "Basslink - About". Retrieved 11 February 2018. 
  8. ^ https://web.archive.org/web/20050902175957/http://www.transmission.bpa.gov/cigresc14/Compendium/KONTI.htm
  9. ^ Bright Future for Long Island
  10. ^ "Power successfully transmitted through NordBalt cable". litgrid.eu. 2016-02-01. Retrieved 2016-02-02. 
  11. ^ http://new.abb.com/systems/hvdc/references/skagerrak
  12. ^ The Norned HVDC Cable Link
  13. ^ [1], Western HVDC Link. Retrieved 23 November 2014.
  14. ^ "Offshore Wind Power Line Wins Praise, and Backing" article by Matthew L. Wald in The New York Times October 12, 2010, Accessed October 12, 2010
  15. ^ Loyd, Linda (April 13, 2012). "Construction under way at new Paulsboro port". Philadelphia Inquirer. Retrieved 2013-07-08. 
  16. ^ "Lower Churchill Project". Nalcor Energy. 
  17. ^ "Cable to the Netherlands - COBRAcable". energinet.dk. 2015-06-10. Archived from the original on 2016-01-20. Retrieved 2016-01-28. 
  18. ^ "Siemens and Prysmian will build the COBRA interconnection between Denmark and the Netherlands". Energinet.dk. 2016-02-01. Archived from the original on 2016-02-02. Retrieved 2016-02-02. 
  19. ^ The EuroAsia Interconnector document
  20. ^ "ENERGY: End to electricity isolation a step closer". Financial Mirror. 2017-10-19. Retrieved 2017-01-04. 
  21. ^ "Cyprus group plans Greece-Israel electricity link". Reuters. 2012-01-23. 
  22. ^ Transmission Developers Inc. (2010-05-03), Application for Authority to Sell Transmission Rights at Negotiated Rates and Request for Expedited Action, Federal Energy Regulatory Commission, p. 7, retrieved 2010-08-02 
  23. ^ Territory study linking power grid between Puerto Rico and Virgin Islands Archived 2011-07-16 at the Wayback Machine.
  24. ^ HVDC Transmission & India-Sri Lanka Power Link 2010
  25. ^ [2]
  26. ^ "Taiwan power company-Taipower Events". Archived from the original on 2014-05-17. 
  27. ^ Carrington, Damian (2012-04-11). "Iceland's volcanoes may power UK". The Guardian. London. 
  28. ^ "Agreement to realize electricity interconnector between Germany and Norway", Statnett 21 June 2012. Retrieved: 22 June 2012.
  29. ^ "Kabel til England - Viking Link". energinet.dk. Retrieved 2015-11-12. 
  30. ^ "Denmark - National Grid". nationalgrid.com. Archived from the original on 2016-03-03. Retrieved 2016-02-03. 
  31. ^ "The world's longest interconnector gets underway". statnett.no. Retrieved 2016-02-03. 
  32. ^ [3], Scottish and Southern Energy. Retrieved 23 November 2014.
  33. ^ FAB website fablink.net, as well as (fr) Interconnexion France Aurigny Grand-Bretagne website rte-france.com, site of Réseau de Transport d'Électricité.
  34. ^ The EuroAfrica Interconnector
  35. ^ Electricity Cable Aims to Link Cyprus, Egypt, Greece, Bloomberg, February 8, 2017
  36. ^ EuroAfrica 2,000MW cable boosts Egypt-Cyprus ties, Financial Mirror February 8, 2017
  37. ^ EEHC, Euro Africa Company sign MoU to conduct a feasibility study to link up Egypt, Cyprus, and Greece, Daily News Egypt,February 6, 2017

External links[edit]