Lillgrund Offshore Wind Farm

Lillgrund is Sweden’s largest wind farm and the world’s third largest offshore wind farm. It is located 7km off the coast of Sweden and 9km off the Denmark coast.

Vattenfall started operations at the 110.4MW Lillgrund offshore wind farm located at Öresund, near Malmö, Sweden, in June 2008.

The wind farm generates 330GWh of electricity per year, sufficient to supply for more than 60,000 houses in Sweden.

The construction of the $1bn Lillgrund offshore wind farm began in 2007. The plant began generating electricity in June 2008.

Lillgrund wind farm make-up

The Lillgrund wind farm comprises of 48 Siemens SWT-2.3-93 turbines and an offshore substation with a 120MVA transformer.

The turbine rotor is a three-blade cantilevered rotor attached to a tubular steel tower. It includes a microprocessor-based industrial controller.

The WebWPS SCADA system of the turbine offers long-distance control and generates reports from a web browser.

The turbine blade is made of fibreglass reinforced epoxy material. The planetary-helical modeled gearbox is attached to rubber bushings.

The generator rotor and stator windings have a higher efficiency rate at partial loads. The generator contains a thermostat-controlled ventilation which performs efficiently even at abnormal temperature levels.

Lillgrund offshore wind farm substation and electrical systems details

The offshore substation at Lillgrund is situated at 25m above the sea level. It is designed as a three floor structure, of which the first floor is an open cable deck. The second floor comprises of rooms for the 120MVA main transformer, 33kV switchgear and a transformer for the local power supply, and emergency diesel generator.

The third floor consists of rooms for the battery back-up system, and the control and monitoring equipment.

The electrical systems at the substation include the 120MVA main transformer and the 33kV switchgear for feeder and local power supply. A mechanical vibration protective device is also installed for prevention of a trip in the electrical equipment.

The 138/33kV 120MVA transformer at Lillgrund is a three-phase, oil immersed transformer manufactured by Siemens. It is cooled by ambient air and is protected against corrosion by special paint. The main transformer is the only transformer and has no back-up.

The 33kV switchgear included in the substation is a Siemens SF6 insulated switchgear type NXPLUS and includes nine panels.

Generation and transmission of power from Lillgrund wind farm

The internal grid of the offshore substation is made up of five feeders comprising of 22km of 33kV sea cables. Each feeder connects nine to ten wind turbines to the offshore substation and the power generated by the turbines is transferred to the substation through 33kV sea cables.

The power generated at the Lillgrund offshore substation is transmitted to EON’s onshore Bunkeflo power station. Three-phase 130kV cables and three single phase onshore 130kV cables are used for the power transmission.

The onshore Bunkeflo substation comprises of a 130kV power system, 2km onshore cable and 7km offshore cable. It is equipped with ION7650 instrument to record the power measurements and the transient faults.

Contractors and suppliers involved with Lillgrund wind farm

The engineering, procurement and construction contract for the Lillgrund offshore wind farm was awarded to Siemens.

Bladt Industries was awarded the contract for the construction of the offshore substation. Mostostal-Chojnice was had the sub-contract for the steel works and painting work.

The contract for wind turbines and electrical system was given to Siemens Wind Power. Siemens sub-contracted ABB for supplying power cables for the power station.

The contract for the foundation works of the wind turbines and the offshore transformer platform was awarded to Pihl & Sohn, and Hochtief Construction.

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