Unprecedented substation design for Hornsea One offshore wind farm

Model of the Hornsea One reactive compensation substation

Model of the Hornsea One reactive compensation substation


Peter Busch Nielsen, Ramboll Oil & Gas

Peter Busch Nielsen

M.Sc., civil and structural eng., Head of Department, Structures, Denmark
T: +45 5161 7238
DONG Energy Wind Power is developing the Hornsea Project One offshore wind farm in the UK. Ramboll carried out the design of a reactive compensation substation for the wind farm, as well as technical assistance during tendering, fabrication and installation.

The world’s largest offshore wind farm development

Hornsea Project One is located 120km off the Yorkshire coast and covers approximately 407 square kilometres. Hornsea Project One has a total capacity of up to 1.2GW, which will make it the world’s largest offshore wind farm once completed. The wind farm will be able to meet the electricity needs of around 800,000 UK homes. Ramboll’s scope of work comprised engineering services related to the conceptual development, detailed design and technical assistance during tendering, fabrication and installation of the substation.

A consequence of moving further offshore

The requirement for an offshore reactive compensation substation is a direct consequence of wind farms moving further offshore. The Hornsea One offshore wind farm will be located in the UK, approximately 120 km (75 mi) off the Yorkshire coast. The 1,2 GW wind farm is expected to host 150-240 turbines, three HVAC substations and the reactive compensation substation. To reduce the power loss in the export cables, the reactive compensation substation is required midway of the export cable between the wind farm and landfall.


How to integrate reactive compensation in design

The high voltage set-up on the platform is the first of its kind on an offshore substation. Hence the project posed a number of interesting challenges for Ramboll’s team of offshore specialist engineers, who investigated a number of solutions on how to best integrate the three shunt reactors that are used to stabilize the voltage during load variations. This included assessing different configurations of high voltage gas insulated switchgear. Moreover, Ramboll designed the topside layout to accommodate for utilities, equipment, SCADA systems, cable deck, laydown area, helideck and emergency accommodation area etc.


A cost-effective structural design for challenging soil conditions

The Hornsea One offshore reactive compensation substation will be standing in 23 m (75 ft) of water. The main geotechnical challenge is extremely weak chalk layers. The topside and jacket design were conceptualized by Ramboll in close collaboration with DONG Energy with the aim of conceiving a cost-effective solution with focus on design optimization and steel weight reduction.


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

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