Offshore substation for Belgian wind farms. Detailed design.

Belgian offshore grid

Belgian offshore grid


Peter Busch Nielsen, Ramboll Oil & Gas

Peter Busch Nielsen

M.Sc., civil and structural eng., Head of Department, Structures, Denmark
T: +45 5161 7238

Ramboll assisted Belgium’s transmission system operator, Elia, with the detailed design of an Offshore Switch Yard platform (OSY). The work was part of a large project that plans to improve wind energy transmission.

Elia is Belgium’s high-voltage transmission system operator and a key player in the European energy market. The company plays a crucial role for both Belgium’s society and economy by powering the community with electricity through approximately 8000 km of lines and underground cables operated across the country.

Producing wind energy smart

Although renewable potential in Belgium is rather low due to the lack of sun and territorial space (IEA), offshore wind farms are a promising source of meeting a growing energy demand. Usually, North Sea wind farms are independently connected to onshore facilities through a substation. To improve offshore wind energy transmission, Elia planned the construction of an offshore grid in the Belgian North Sea to connect four planned offshore wind farms to the onshore grid connection point in Zeebrugge. The wind farms won’t be constructed simultaneously therefore the offshore grid will take on a modular concept that is flexible and allows a multiphase development. The whole setup is facilitated by an OSY substation that is able to receive power not only from one, but from multiple wind farms regardless of the time of construction. This will ensure fewer cables on the seabed and less costs in terms of construction and maintenance.

Delivering a design based on time and cost effectiveness

Ramboll was awarded the detailed design of the OSY platform as well as an optimisation study, an operation and maintenance study, and procurement. As basis for the detailed design, Ramboll defined philosophies and strategies for safety, and operation and maintenance as well as requirements for mechanical completion and commissioning. The KPI and focus for the design of the OSY substation was related to providing a design minimising the time and cost for fabrication.

The OSY platform, located 45 km (28 miles) off the Belgian coast at water depths of 34 metres (111.5 feet), was designed for unmanned operation and sits on a four-legged jacket. The work included geotechnical interpretation as basis for the foundation and jacket detailed design ready for fabrication. The topside comprised a full multi-discipline design including a structural design ready for fabrication, and was configured with three fully closed deck levels and roof deck with an integrated helideck, crane, and lay down areas. The interior was equipped with a 220kV gas insulated switch gear, as well as multiple wind farm cable-connections. Ramboll also performed detail design of all mechanical, piping and electrical, instrument and telecom systems.

Promising future ahead

Elia’s future plans also include connecting the modular offshore grid to an international platform with direct-current (DC) connections that make it possible to transmit greater quantities of power, including to other countries that plan to develop a similar infrastructure in their North Sea territorial waters. In addition, these connections will allow wind energy to be stored in case of any surpluses, securing Belgian consumers with sustainable energy for days when the wind is not generous enough.


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Company registration

Company registration

Ramboll UK Limited. Registered in England & Wales. Company registration no. 03659970. Registered office: 240 Blackfriars Road, London SE1 8NW

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