Wolfe Island Wind Project Submarine Power Cable

A submarine power cable is a transmission cable for carrying

electric power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions o ...

below the surface of the water.Underwater Cable an Alternative to Electrical Towers
Matthew L. Wald, ''

New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid d ...

'', 2010-03-16, accessed 2010-03-18. These are called "submarine" because they usually carry electric power beneath

salt water Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

(arms of the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

strait A strait is an oceanic landform connecting two seas or two other large areas of water. The surface water generally flows at the same elevation on both sides and through the strait in either direction. Most commonly, it is a narrow ocean channe ...

s, etc.) but it is also possible to use submarine power cables beneath

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

(large

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

s and

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

s). Examples of the latter exist that connect the mainland with large islands in the

St. Lawrence River The St. Lawrence River (french: Fleuve Saint-Laurent, ) is a large river in the middle latitudes of North America. Its headwaters begin flowing from Lake Ontario in a (roughly) northeasterly direction, into the Gulf of St. Lawrence, connecting ...

Design technologies

The purpose of submarine power cables is the transport of

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

high voltage High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, ''high voltage'' refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant spec ...

. The electric core is a concentric assembly of inner conductor,

electric insulation An electrical insulator is a material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—semiconductors and electrical conductor, conductors—con ...

and protective layers (resembling the design of a

coaxial cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...

). Modern three-core cables (e.g. for the connection of offshore wind turbines) often carry

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

s for data transmission or temperature measurement, in addition to the electrical conductors.

Conductor

The conductor is made from

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

or aluminum wires, the latter material having a small but increasing market share. Conductor sizes ≤ 1200 mm² are most common, but sizes ≥ 2400 mm² have been made occasionally. For voltages ≥ 12 kV the conductors are round, so that the insulation is exposed to a uniform

electric field gradient In atomic, molecular, and solid-state physics, the electric field gradient (EFG) measures the rate of change of the electric field at an atomic nucleus generated by the electronic charge distribution and the other nuclei. The EFG couples with the ...

. 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

Three different types of

around the conductor are mainly used today.

Cross-linked polyethylene Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, ins ...

(XLPE) is used up to 420 kV system voltage. It is produced by

extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...

, with an 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 The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

insulation fluid (

mineral oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...

or synthetic). A central oil channel in the conductor facilitates oil flow in cables up to 525 kV for when the cable gets warm but rarely used in submarine cables due to

oil pollution An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

risk with cable damage. 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. Mass-impregnated insulation can be used for massive

HVDC A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curren ...

cables up to 525 kV.

Armoring

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

Most electrical power transmission systems use alternating current (AC), because

transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...

s can easily change voltages as needed.

High-voltage direct current A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curre ...

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 Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...

of the cable would require too much additional charging current. The inner and outer conductors of a cable form the plates of a

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...

, 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

Alternating current cables

Alternating-current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which ...

(AC) submarine cable systems for transmitting lower amounts of

three-phase electric power Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, transmission, and distribution. It is a type of polyphase system employing three wires (or four including an optional neutral ...

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 An anchor is a device, normally made of metal , used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin ''ancora'', which itself comes from the Greek ἄγ ...

carelessly dropped onto it. The fourth cable can substitute for any one of the other three, given the proper

electrical switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

ing system.

Direct current cables

Submarine power cables under construction

Atlantic Wind Connection Atlantic Wind Connection (AWC) was a proposed electrical transmission backbone by Trans-Elect Development Company that could be constructed off the East Coast of the United States to service off-shore wind farms. Google Energy, the investment ...

between

Delaware Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent Del ...

and

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

, potentially between

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

and

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

"Offshore Wind Power Line Wins Praise, and Backing"
article by Matthew L. Wald in ''

The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...

'' October 12, 2010, Accessed October 12, 2010 * 500 MW capacity, 165 km DC Maritime Transmission Link between the Canadian province of

Newfoundland and Labrador Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

and the province of

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

. * On February 1, 2016 Danish and Dutch operators (Energinet.dk and

TenneT TenneT is a transmission system operator in the Netherlands and in a large part of Germany. ''TenneT B.V.'' is the national electricity transmission system operator of the Netherlands, headquartered in Arnhem. Controlled and owned by the Dutch g ...

) awarded construction contracts to

Siemens Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad. The principal divisions of the corporation are ''Industry'', '' ...

and

Prysmian Prysmian S.p.A. is an Italian company with headquarters in Milan, specialising in the production of electrical cable for use in the energy and telecom sectors and for optical fibres. Prysmian is present in North America with 23 plants, 48 in Eur ...

for COBRAcable, a 294 km submarine cable to provide the two countries with 700 MW transmission at 320 kV DC starting in 2019. *

Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe *Norwegians, both a nation and an ethnic group native to Norway *Demographics of Norway *The Norwegian language, including the ...

and German power companies have built

NORD.LINK NordLink is a subsea 1,400 megawatt (MW) HVDC power cable between Norway and Germany, opened in May 2021. The over long cable operates at a voltage of 500 kV DC. The cable enables Deutsche Bahn to buy the full production from M� ...

, a submarine cable transmitting up to 1,400 MW between the two countries by 2018. As of 2021, it is in testing. * British and

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...

power companies ( National Grid and

Energinet.dk Energinet is the Danish national transmission system operator for electricity and natural gas. It is an independent public enterprise owned by the Danish state under the Ministry of Climate and Energy. Energinet has some 1150 employees, a ...

, respectively) are building

Viking Link Viking Link is a 1,400 MW HVDC submarine power cable under construction between the United Kingdom and Denmark. Current status Land cables and submarine cables are being installed since 2020 and expected to finish in 2023. As of August 2022 Den ...

, a 740 km cable to provide the two countries with 1,400 MW transmission by 2022. *Black Sea submarine electric cable with capacity of 1 GW and voltage of 500 kV will transfer green electricity from Azerbaijan through Georgia, Romania, Moldova to the EU. It is estimated to be approximately 1100 km in length and to be built in late 2029.

Proposed submarine power cables

Australia–ASEAN Power Link The Australia–Asia Power Link (AAPowerLink) is a proposed electricity infrastructure project that is planned to include the world's largest solar plant, the world's largest battery, and the world's longest submarine power cable. A solar farm ...

(AAPL), or the Australia–Singapore Power Link (ASPL), is a proposed electricity infrastructure project that is planned to include the world's longest submarine power cable. A solar farm in Northern Territory, Australia, will produce 10 gigawatts of electricity, most of which will be exported to Singapore by a 4,500 km (2,800 mi) 3 GW HVDC transmission line. *

EuroAsia Interconnector The EuroAsia Interconnector is a HVDC interconnector between the Greek, Cypriot, and Israeli power grids via the world's longest submarine power cable ( from Israel to Cyprus and from Cyprus to Greece, for a total of ). Connecting Kofinou, Cypru ...

, a 1,520 km submarine power cable, reaching depths of up to under sea level, with the capacity to transmit 2,000 megawatts of electricity connecting Asia and Europe (Israel–Cyprus–Greece)The EuroAsia Interconnector document
''www.euroasia-interconnector.com'' October 2017. *

Champlain Hudson Power Express The Champlain Hudson Power Express (CHPE) is a proposed high-voltage direct current (HVDC) underwater and underground power cable project project linking the Quebec area to the New York City neighborhood of Astoria, Queens. Following completion of ...

, 335-mile line. The Transmission Developers Company of

Toronto, Ontario Toronto ( ; or ) is the capital city of the Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the most populous city in Canada and the fourth most populous city in North America. The city is the ancho ...

, is proposing "to use the

Hudson River The Hudson River is a river that flows from north to south primarily through eastern New York. It originates in the Adirondack Mountains of Upstate New York and flows southward through the Hudson Valley to the New York Harbor between N ...

for the most ambitious underwater transmission project yet. Beginning south of

Montreal Montreal ( ; officially Montréal, ) is the List of the largest municipalities in Canada by population, second-most populous city in Canada and List of towns in Quebec, most populous city in the Provinces and territories of Canada, Canadian ...

, a 335-mile line would run along the bottom of

Lake Champlain , native_name_lang = , image = Champlainmap.svg , caption = Lake Champlain-River Richelieu watershed , image_bathymetry = , caption_bathymetry = , location = New York/Vermont in the United States; and Quebec in Canada , coords = , type = , ...

, and then down the bed of the

Hudson Hudson may refer to: People * Hudson (given name) * Hudson (surname) * Henry Hudson, English explorer * Hudson (footballer, born 1986), Hudson Fernando Tobias de Carvalho, Brazilian football right-back * Hudson (footballer, born 1988), Hudso ...

all the way to

New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...

." * Power Bridge,

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

* Power Bridge,

State of Maine Maine () is a U.S. state, state in the New England and Northeastern United States, Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and territories of Canad ...

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

to the

Virgin Islands The Virgin Islands ( es, Islas Vírgenes) are an archipelago in the Caribbean Sea. They are geologically and biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Rico Trench and St. Croix ...

* 400 kV HVDC

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

* 220 kV HVAC, 225 megawatts, 117 km Malta–Sicily interconnector between Magħtab, Malta, and

Ragusa, Sicily Ragusa (; scn, Rausa ; la, Ragusia) is a city and ''comune'' in southern Italy. It is the capital of the province of Ragusa, on the island of Sicily, with 73,288 inhabitants in 2016. It is built on a wide limestone hill between two deep valley ...

. * The 58.9-km, 161-kV

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

Island to the

Penghu Islands The Penghu (, Hokkien POJ: ''Phîⁿ-ô͘'' or ''Phêⁿ-ô͘'' ) or Pescadores Islands are an archipelago of 90 islands and islets in the Taiwan Strait, located approximately west from the main island of Taiwan, covering an area ...

submarine power cable system (T–P-cable), the first submarine project of the

Taiwan Power Company The Taiwan Power Company (, Taipower; ) is a state-owned electric power industry providing electricity to Taiwan and off-shore islands of the Republic of China. History Taipower was established on 1 May 1946. Its origins can be traced to 1919 ...

(Taipower) at this level, scheduled for completion in 2014. On 24 December 2010, the '' Taiwan-Penghu Undersea Cable Project'' of

Taipower The Taiwan Power Company (, Taipower; ) is a state-owned electric power industry providing electricity to Taiwan and off-shore islands of the Republic of China. History Taipower was established on 1 May 1946. Its origins can be traced to 1919 ...

was approved to connect the

electrical grid An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...

in Taiwan Island to the Penghu Islands. * The British and Icelandic Governments are supposedly in "active discussion" to build a cable (

Icelink Icelink is a proposed electricity interconnector between Iceland and the United Kingdom via Great Britain. At , the 8001,200MW high-voltage direct current (HVDC) link would be the longest sub-sea power interconnector in the world. The project pa ...

) between

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

and

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

to carry

geothermal power Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 2 ...

to Scotland. It would be 1,000 to 1,500 km long "and by far the longest in the world." assuming a longer cable not yet built like the proposed 4,200 km Australia–Singapore cable * FAB between

Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...

and

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

via Alderney Island in the

Channel Islands The Channel Islands ( nrf, Îles d'la Manche; french: îles Anglo-Normandes or ''îles de la Manche'') are an archipelago in the English Channel, off the French coast of Normandy. They include two Crown Dependencies: the Bailiwick of Jersey, ...

. *

EuroAfrica Interconnector EuroAfrica Interconnector is a HVDC interconnector and submarine power cable between the Greek, Cypriot, and Egypt power grids.Liu Ko Ngam and

Pak Sha Tau Tsui Pak or PAK may refer to: Places * Pakistan (country code PAK) * Pak, Afghanistan * Pak Island, in the Admiralty Islands group of Papua New Guinea * Pak Tea House, a café in Lahore, Punjab, Pakistan Arts and entertainment * PAK (band), an Ame ...

Kat O Kat O () also named Crooked Island, is an island in Northeast Hong Kong. Administration Administratively, Kat O is part of North District. It is a recognized village under the New Territories Small House Policy. Geography Kat O is located in ...

, Northeast Hong Kong, approximately 880 m in length.

References

External links

Subsea Cables UK - An organisation of submarine cable owners, operators and suppliers aimed at promoting marine safety and protecting cable installations on the UK continental shelf

The International Cable Protection Committee

Subsea Cables UK article on Submarine Power Cables

Export cables from Offshore Wind farms to Offshore substations

Transmission cables from Offshore converter to shore

(Cross sections of historic power cables) {{DEFAULTSORT:Submarine Power Cable Electric power transmission de:Seekabel#Gleichstromkabel