LONDON — HVDC significantly reduces transmission losses and is widely considered to be the only viable solution for economical, low-loss transmission of power via cable longer than around 80 km, as with longer AC cables a significant proportion of the electrical energy transmitted is lost due to reactive power requirements.
This latest contract, which ABB says is the largest power transmission order in its history, will deploy what it says is the world’s largest offshore HVDC system, at more than 900 MW and 320 kV. The contract is on behalf of the Dutch-German transmission system operator TenneT.
ABB emphasises the key advantage of the technology, saying that electrical losses will amount to less than one percent per converter station from the 400-MW Gode Wind II, and other wind farms, to an offshore HVDC converter station, which will be used to transmit DC electricity to the onshore HVDC station at Dörpen on the German coast via 135 km of underwater and underground cables. The Dörpen station will feed power to the grid.
Scheduled to be operational in 2015, under the terms of the contract ABB will design, engineer, supply and install the offshore platform, the offshore and onshore converter stations and both the land and sea cable systems.
“Offshore wind power is emerging as a major source of large-scale renewable energy in Europe to help meet emission targets and lower environmental impact,” said Peter Leupp, head of ABB’s Power Systems division, adding that the company has invested significantly in these technologies.
The company further claims that its HVDC Light technology offers environmental benefits, such as neutral electromagnetic fields and compact converter stations.
This is the third recent offshore wind connection order for ABB in Germany, following the 800-MW Dolwin 1 link awarded last year and previously the BorWin 1 project.
In February ABB also won a $180 million order from utilities Statnett of Norway and Energinet.dk of Denmark to supply an HVDC Light solution to support the interconnection of the Norwegian and Danish power grids. The 500-kV underwater link is a new record in transmission voltage using this technology, the company claims, and will boost transmission capacity between the mainly hydroelectric-based Norwegian system and the wind and thermal power-based Danish system. It will enable both networks to add more renewable energy to their energy mix, and to use electricity more efficiently, ABB says.
It will design, supply and commission two 700-MW converter stations located at either end of the 240 km-long interconnector, and will be situated at the same site as the existing converter stations for Skagerrak 1-3 previously supplied by the company, in Kristiansand, Norway and Tjele, Denmark. The bipolar link, scheduled for commissioning in 2014, will be operated with the Skagerrak 3 transmission system.
Commenting on the technology, Leupp said: “It will also reduce the impact of power system disturbances and contribute to the stability and reliability of the grids. The higher voltage level will also help minimise transmission losses.”
Leupp continued on the technology, adding: “It will also reduce the impact of power system disturbances and contribute to the stability and reliability of the grids. The higher voltage level will also help minimise transmission losses.”
Other recent orders for large-scale ABB HVDC systems include a $700 million order for a 325 kV HVDC Light power transmission link connecting three offshore wind farms in the North Sea to the German power grid.
While ABB is one of the leading proponents of HVDC technology, it is far from the only game in town with other energy engineering majors having developed their own solutions.
Germany’s Siemens, for example, has also revealed a series of recent contracts based on its HVDC systems to support renewable energy installations.
High Voltage Direct Current has emerged as a strong component in the development of offshore wind power (Source: ABB)
For instance in August, and working in consortium with the Italian cable manufacturer Prysmian, Siemens Energy said it was erecting HelWin 2, the HVDC link between the North Sea offshore windfarm Amrumbank West and the onshore grid. Again the customer is TenneT TSO GmbH and the order is worth approximately €600 million ($816.4 million) to the consortium.
Prysmian will provide complete supply, installation and commissioning of the submarine and land cable connections as part of a larger contract, while Siemens will deliver the Voltage Sourced Converter (VSC) system, rated at 690 MW. The turnkey connection will link the offshore wind park Amrumbank West, located about 55 km offshore in the North Sea, to the mainland.
The link is scheduled to be operational by 2015, grid-connecting the 300-400-MW Amrumbank West wind farm project, which is to be located about 35 km north of Helgoland, and 37 km west of the North Frisian island of Amrum.
Power will be transmitted at 320 kV via a submarine high-voltage cable from the feed-in point on the platform to the grid connection point in Büttel, northwest of the city of Hamburg, over 130 km away.
Together with the Meerwind and North Sea East offshore wind farms, Amrumbank West is part of the North Sea cluster HelWin. Central to the HelWin 2 link is the offshore converter platform HelWin beta, on which the Siemens HVDC Plus system is installed. Siemens is responsible for the turnkey supply of the fully equipped floating and self-erecting platform.
TenneT’s German group Transpower, which it acquired in 2009, has now ordered its third offshore grid connection from the Siemens Energy and Prysmian Powerlink group. The HVDC connection “BorWin2” has a design capacity of 800 MW will connect the wind farms Global Tech 1 and Veja Mate to the onshore transmission grid.
Together with the additional services separate from the contract with Siemens/Prysmian, Transpower’s investment for BorWin2 will be worth around €800 million.
Completion of the grid connection, stretching some 200 km to a substation in Diele, close to Papenburg, is planned for spring 2013. The substation for the first HVDC offshore connection, the €400 million, 400-MW project “BorWin1” which was completed in 2009, is also located in Diele.
In a related development, Siemens Energy recently extended its transformer production location in Guangzhou, China by setting up a new facility for the production of 800-kV converter transformers intended to serve the future needs of the Chinese market and the wider Asia-Pacific region.
In addition to HVDC transformers, power transformers with ratings up to 1400 MVA will also be produced at the new facility. “With our new facility we’re not only extending our global network of HVDC transformer factories and expanding our product portfolio in Asia. Through the local production of HVDC transformers we’re also enhancing our competitiveness in the field of HVDC transmission in China,” said Jürgen Vinkenflügel, chief executive officer of the Transformers Business Unit of Siemens Energy.
And backing this up, Siemens says it is to supply key components for two HVDC transmission projects — Nuozhadu-Guangdong and Xiluodu-Guangdong — in southern China. The purchaser is China Southern Power Grid Co.
Nuozhadu-Guangdong will have a transmission capacity of 5 GW at a voltage of 800 kV, while Xiluodu-Guangdong is to have an overall capacity of 6.4 GW at 500 kV, Siemens says. The total order value for the company is approximately €250 million and commissioning of the systems is scheduled for 2013.
Large-capacity hydroelectric plants such as Nuozhadu and the 12.6 GW Xiluodo in southwest China will use the low-loss transmission provided by the new links to bring energy to the megacities Guangzhou, Jiangmen, Dongguan and Shenzhen.
For the Nuozhadu-Guangdong 800 kV HVDC bipole system, Siemens, together with its Chinese partners, will supply the converter valves both for the sending station in Puer in the province of Yunnan and for the receiving station in Jiangmen, Guangdong Province, a distance of 1451 km.
The Xiluodu-Guangdong project is a double 500 kV bipole system with a transmission capacity of twin 3,200-MW systems. For this project Siemens, again together with Chinese partners, will supply the converter valves for the sending station in Zhaotong, near the Xiluodu hydro power plant in the Yunnan/Sichuan region, and for the receiving station in Conghua of Guangdong province, a distance of 1,286 km.
In late December 2009, Siemens and China Southern Power Grid put into operation the first pole of an HVDC system with a transmission capacity 5 GW and covering a distance of over 1,400 kilometers. And, in April, together with the operating company BritNed Development Ltd., Siemens commissioned the 260 km BritNed HVDC transmission link between the UK and the Netherlands. BritNed — itself a joint venture of National Grid and TenneT — operates the link which has a transmission capacity of 1,000 MW at 400 kV.
As with the ABB development in Norway/Denmark, late last year Siemens also secured a contract for its HVDC systems which exploits another key advantage of the technology in that it allows asynchronous grids to effectively phase frequencies.
The company is building converter stations in Püssi, Estonia, and Anttila, Finland, for a new transmission link between the two nations. EstLink 2 will have a transmission capacity of 650 MW at 450 kV and will comprise 14 km of overhead, a 145-km submarine cable across the Gulf of Finland, and a 12-km buried cable. The development will increase the capacity for transmission between the Baltic and Nordic countries from 350 MW to 1,000 MW, making the power supply more reliable for the Fingrid utility based in Helsinki and the Estonian power network operator Elering, based in Tallinn.
Partially funded by the EU, the contract is worth some €320 million, with Siemens’ share about €100 million of that. The converter stations are planned to go into operation early in 2014.
Taking the grid integration idea just one step further comes the Tres Amigas ‘SuperStation’ project in New Mexico, US. Once completed this transmission hub will ultimately interconnect America’s three primary electricity grids, the Eastern (Southwest Power Pool), Western (Western Electricity Coordinating Council) and Texas (Electric Reliability Council of Texas) networks.
In April Alstom Grid announced a contract worth approximately €150 million ($204.1 million) by Tres Amigas LLC for HVDC converters and automation technology as well as high availability system maintenance services for the first stage of the project.
Under the contract, Alstom Grid will supply a 750-MW, 345-kV converter scheme utilising its Voltage Source Converter (VSC) technology.
With a clutch of the major players offering commercial HVDC systems it is perhaps of little surprise that a new report from Pike Reaserch concludes: “The demand for these products is rapidly moving beyond the traditional role slotted for high-voltage submarine cables, connecting islands to nearby national grids. The usage of high-voltage submarine cables for grid interconnections and connecting offshore wind farms to nearby landmasses is on the rise.”
However, the report, HVDC and HVAC Submarine Power Cables: Supply Constraints, Demand Drivers, Technology Issues, Prominent Projects, Key Industry Players, and Global Market Forecasts also issues a warning. It suggests that with only a handful of manufacturers capable of producing and installing such systems, and indications of a limited supply chain for cables, capacity constraints could become an issue, particularly in light of the increased demand that offshore renewable energy production and grid interconnection will place on the market.
The report concludes: “The constraints on the supply chain don’t stop with the manufacturers. The site engineering companies and cable-laying ships required are highly specialised and also in limited supply. As countries all over the world experience an increased need for advanced grid connections and renewable power, cable manufacturers will need to significantly increase their production capabilities to keep up with the steady demand growth in the years ahead.”