Horns Rev Newsletter
- June 2002
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Cable
pulling and connecting of sea cable The activities at the Horns Rev construction site are now in highest gear and the contractors are working intensively with the foundation pile driving and the turbine installation. And the internal cable pulling for the wind farm has been initiated. Late May, Nexan, the cable supplier, started pulling the cables, which connect the turbines and the substation. Cable pulling and connecting are scheduled to follow the turbine installation to avoid damaging of the cables. The cables are trenched at a depth of 1-2 meters in the seabed by a cable-laying vessel. At the turbines the cable is pulled into a protecting J-tube and guided to the turbine where it is connected to the turbine's high-voltage high-voltage system. At the seabed, divers make sure that the cable enters the J-tube correctly. At the substation, the cable is guided into the J-tube and connected to the transformer via a 34-kV switchgear. The turbines are grouped in five radial configurations of 16 turbines each. 34 kV voltage applies from the turbines to the substation's transformer. After the transformer, the voltage is 150 kV. The cable work includes the
submersion of the cables, which connect the five turbine groups to
the transformer at the substation as well as the submersion of the
cables in-between the individual turbines of the wind farm. The
optimal cable design has been chosen, taking into account both
technical and economic aspects. The final choice fell on
3-conductor, 400 mm2 copper PEX cables for the cables
from the groups to the substation and on 150 mm2 copper
cables for the internal cables between the individual turbines. Only
one 95-mm2 copper cable is connected to the turbine at
the end of each row. By 25 June 2002 cables have been connected for 16 turbines and the initial production from this wind farm is expected to be brought ashore in mid-July 2002. All turbines are scheduled to be connected by the end of October. |
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Status: turbine erection The erection of the turbines is well under way and Vestas and A2SEA, Vestas' sub-supplier, now work simultaneously on two turbines from each of the two crane vessels in operation. This ensures efficient installation work in that each of the vessels is capable of erecting one turbine each day, weather conditions permitting. By June 25 a total of 26 turbines were erected. As the crane vessels continue erecting turbines, Vestas' staff are making the final installations inside the already erected turbines and preparing them for operation. The staff are transferred to the turbines from the crane vessels by boat.
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Status: foundations
The foundation pile driving is on schedule and more than 60 % of the foundations are installed. By 25 June a total of 49 piles had been driven into the seabed and transition pieces had been installed on 45 of these. At the current speed of driving and with acceptable weather conditions, MT Højgaard, the foundation contractor, expects the drive the last foundation piles in early August. |
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Weather
forecast programme Since the installation work at Horns Rev very much depends on calm weather it is of utmost importance to be able to make precise weather forecasts. For this purpose, Tech-wise A/S, which is a subsidiary of Elsam A/S, has developed a reliable weather forecast programme which is often used by the partners of the Horns Rev project. The programme is based a weather forecast programme developed by the Danish Meteorological Institute and on a wave forecast model developed by DHI Water & Environment. Combined with local measurements of actual wind, wave and current conditions at Horns Rev this programme produces reliable forecasts for the area at Horns Rev with a 48-hour time frame. The forecasts are made available to the project's contractors and are used frequently in connection with the scheduling of tasks. |
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Monitoring
of the environment
The environmental monitoring programme at Horns Rev is according to schedule. The movements of the seals in the area is still monitored via satellite. To be able to register the right position of the seal it must emerge from the sea for some time and therefore there might be some problems with locating the seals from time to time. Birds visiting the area around the Horns Rev construction site are observed and their whereabouts are presently being registered from the air. In autumn 2002 the ornithologists would like to find out how the birds react to the wind turbines. It is therefore important for them to be able to estimate and calculation the risk of collision for the individual kinds of birds. Will migrating seabirds pass the wind farm while the turbines are in operation? - or do they prefer to fly by or over the wind farm? And, not least will they be attracted to the marking (lights) of the turbines during night time? These are some of the questions which should be answered during monitoring. However, these questions are not answered by performing bird counts. The birds must be visually observed and therefore, the ornithologists have carried out initial inspections of the wind farm with a view to finding suitable spots from where the park can be observed. In late August the first observations will take place. In spring 2003 radar surveillance equipment may be installed at the substation so that bird migration and possible collisions can be monitored from ashore.
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Elsam A/S
Overgade 45
DK-7000 Fredericia
Phone: +45 76222000
Fax: +45 76221962
www.elsam.com