Offshore cabeling: Cabling maintenance planning processes


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Offshore cabeling: Cabling maintenance planning processes

  1. 1. Cabling, maintenance and planning processes for offshorewind farmsBy Al TuttleDespite the battles that were fought about the safety and viability of deep sea windfarms, builders are getting international permits for more turbines. They are beingbuilt or are approved in some of the angriest waters north of the equator. Comparedto rather mild waters of New England, where the first wind farm on the east coast ofNorth America has been approved off Massachusetts, the North Sea and Baltic Seaare more treacherous and unpredictable.Europe has over 4,000 wind turbines and manufacturing companies of components,turbines, seagoing vessels and cables are learning more each year about theprocess of building a wind farm, according to experts in the undersea cable field.Power transfer cables are very specialized and made only by a few companiesaround the world. Every wind farm uses a complex combination of undersea, buriedcables, turbine connectors, splices and connections at an at-sea substation.One challenge in the arena of wind technology at sea is developing and refining bestpractices for installing arrays of cables in giant fields of wind turbines, said JoelWhitman of Global Marine Systems. Global Marine is one of the world’s largestmarine cable layers and offshore service providers. (1) The company has worked onsome of the biggest wind farms in the world, particularly in European waters.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  2. 2. “There are significant problems when laying cable in the ocean that everyone is stilltrying to solve,” Whitman said. Installing cable along the seabed meansencountering landscapes as varied as those on land. With miles and miles of seabedto cross, and with cable to be buried two meters deep, the possibilities forencountering obstacles that slow or stop progress are multiplied. Companies likeGlobal Marine use the most sophisticated electronic equipment available to map andanalyze the seabed. There are steep hills, rugged bottoms and material that rangesfrom mud and silt to hard clay and rock. There are always a great number of unknowns when a project the size of a wind farm at sea is being developed. While the water is generally 70 meters deep or shallower, the cable is exposed to powerful stress forces when installed and being buried, or while connected to the Whitman said. Some of the arguments used against giant wind farms are ironically environmentally based. As a power source born and developed in part because it uses no or very little fossil-based fuels, the natural view of wind power is that it is supremely clean and friendly to every environment. Since each tower is the size of the Statue of Liberty and a field can be 100 square miles, some groups against seaborne wind power say that the Photo courtesy Siemens energy needed to create all the parts, put them in theocean and connect them, is more than the energy the wind farm can create inseveral years’ production. These groups decry the pollution supposedly created bythis manufacture and construction. They also claim that in spite of the 4,000 unitsworking in Europe, none of the electric rates paid in affected countries have gonedown. Some people also argue that fishing areas and shipping lanes are threatenedby giant wind farms.Extensive right-of-way negotiations can solve many of these navigation problems.Those negotiations must be part of a deeper research and development plan for------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  3. 3. each project. Wind farms are still trying to reach a point of profitability, Whitmansaid, because the companies and consortiums put together to build and operatethem have not planned every step completely enough. More companies workingtogether will benefit every wind project, he said. These larger groups of manpowerand machine power, combined with more experts researching every part of theplan, will make every project more complete before any work is done in the water.“When everything is running well, the whole system is profitable,” he said.Seaborne wind farms have no construction impact on property (as do land-basedfarms), no noise pollution problems and are generally not a threat to visibility.However, many of the projects Global Marine has been involved with run intoproblems that take a lot of money to fix. The turbines are linked in a line, so that if one goes out of service due to a cable problem, the rest in front of the down turbine all stop working. “If the last turbine is out, it is the only one out and is not as much of an emergency as is a turbine that goes down and stops all the rest with it,” he said. The result is an emergency need for cable, crews and ships. Photo courtesy Siemens The supply of cable on hand is critical for repairs. Whitman’s company has been involvedin projects that did not have enough backup cable on hand. In one instance,Whitman said that the wind farm operators had asked for only one mile of cable bestored as inventory for an emergency. That is less than one length of connectioncable between two turbines. When a turbine cable far up the line failed, thecompany waited weeks for more repair cable to be made, Whitman said. So anextremely expensive supply chain problem occurs in the repair and maintenancearea when not enough cable (and other contingent supplies) are not kept on hand.Regular maintenance has not been addressed in depth either, according toWhitman. Checking connections and cable is not a perfect art, but is necessary andis an area that needs more specialized equipment. Every tower is made in fourparts: the original electrical connection is made before the turbine is placed on the------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  4. 4. transition piece. After the turbine is put onto the assembly, that connectionbecomes more difficult to inspect and replace or repair. The same is true for cablerunning between turbines, connecting them in a line, and for cable running to andaway from the substation. When cable is inspected and tested at the factory, it iseasier to detect defects visually. After cable is buried and tests are completed forevery section, the cable becomes exposed to the underwater environment on apermanent basis. This is a challenge to the rugged reliability of the cable,connections and turbine construction.There are only a handful of companies supplying undersea power cable. Theseagoing environment is far different from land-based wind farm tracts. There arepluses and minuses for either environment: the sea has no surface terrain but theseabed has a variety of landscapes. The cables are made under strict quality andenvironmental rules by companies like nkt cables of Denmark (2), which is a worldleader not only in cable manufacturing but in research, safety and technology. Thecompany is researching more durable materials for use in cabling. They are alsovery concerned about using as environmentally friendly materials as possible. nktcable replaced dangerous materials like lead and PVC in its cable products.It is becoming more obvious that not only are wind farms here to stay, but more,bigger projects are on the way. In Denmark, Germany and England, projects areplanned using even bigger wind fields and bigger turbines. In the case of farmsplanned for the Baltic and North Seas, extremely complex connections and farmhubs are planned, with power going to several countries. (3) These projects addlayers of complexity to the entire construction process: supply and security, landand water lease, manufacturing prediction, quality support and more. According toexperts like Joel Whitman, this complexity demands that the partners in the projectbroaden the scope of planning and consider more redundancies than have beenincluded thus far. One of the critical areas that needs a longer look is maintenance.Now, many years after the building of the first offshore wind farms, evidence isbuilding about the need for more comprehensive maintenance programs and backup------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  5. 5. equipment. According to one report (4), these huge yet extremely precise machinesare beginning to need repair or replacement. The report notes that turbines in theNorth Sea are expected to last 20 years but some are failing at age eight. It couldsimply be the very difficult North Sea conditions, but those conditions are prevalentin other European waters. Finally, the report notes that the expenses of buildingeach completed turbine has exceeded estimates while output has been less thanexpected, in megawatts/unit.As the size of farms increases and more farms are planned, the final maintenanceand contingency inventory and funding must be increased. That comes from betteroverall long range planning. The more experience operating consortiums have atmaintaining an average wind farm, the better they will be able to anticipatemaintenance problems.Al TuttleFreelance EditorAl Tuttle is news and features editor whose experience includes Media NewsGroup, Reed Elsevier and New York Times New England. He specializes in industrialand commercial writing. He was in sales for industrial distribution companies andmanufacturers for 15 years. 1. e 2. ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  6. 6. 3. ports/OffshoreGrid__report.pdf 4. for-offshore-wind-farms/ Want to know more about offshore cabeling? Check out our Download Centre, where you will find more articles, white papers and interviews regarding this topic: ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: