CABLE INSTALLATION FEATURE
BELWIND OFFSHORE A CASE STUDY
The Belwind offshore wind farm is located in the North Sea, about 50 kilometers off the coast of Belgium. In a first building phase, 55 3MW turbines have been installed, equaling a total output power of 165 MW. The farm was made fully operational in December 2010.
INNOVATIVE GRID CONNECTION CONCEPT
In order to get the generated electrical power on the onshore grid of Belgian transmission system operator (TSO) ELIA, an innovative grid connection concept was used.
All wind turbines are connected at 33-kV level to the offshore high-voltage substation (OVHS). The main component of that substation is a 3-winding 33/150kV step-up transformer. From the OVHS, the power is transported to a 150kV onshore substation and there fed to the 380kV ELIA transmission grid.
The new grid connection concept used for the Belwind project is shown below. In this concept, there is no static VAR compensator onshore. The required capability curve by ELIA is met due to...
• The reactive power of the export cable
• The regulating capabilities of the wind turbines
• The installation of offshore reactors
ONSHORE TRANSFORMER Onshore, a booster transformer has been added to the system. This transformer is a series-compensated 150/150kV autotransformer and has 2 main functions. The most important function is the voltage regulation of the 33kV offshore grid. In order to benefit from the reactive power capabilities of the wind turbines, this voltage needs to be constant with only small deviations (+/- 1%) of the nominal voltage.
A second function of the booster transformer is to limit the switch-in current as well as voltage transients occurring when the onshore high- voltage breaker is closed. Therefore, this transformer is equipped with a soft- closing device. This device is connected to an internal circuit at a medium voltage level.
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www.windenergynetwork.co.uk
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