Borssele Alpha AC Offshore High Voltage Substation

The Offshore High Voltage Substations

Borssele Alpha and Beta are required to link the wind farms built offshore in the Dutch North Sea. The Borssele Alpha project, followed with the Borssele Beta project, are the first large-scale grid connections to be constructed under the National Energy Agreement for offshore wind farms in the Netherlands.

Piles: 61 m each

Field Power capacity: 2 x 350 MW each

HSM Offshore, has taken on the engineering, procurement, construction, transport, installation, connection and testing of the offshore transformer station under an EPCI contract. Iv-Offshore & Energy is the subcontractor for this project and is responsible for the design, engineering and procurement support, including the integration of the TenneT free issued High Voltage components and the balance of plant materials.

The detailed design and engineering includes both the steel jackets with skirt pile foundations and the lift installed topsides.

Iv-Offshore & Energy is responsible for the procurement of all necessary services, materials, and equipment and the onshore and offshore commissioning of all systems of the jackets and topsides, including the TenneT supplied HV equipment. Iv-Offshore & Energy also manages the interfaces with the other parts of the grid connection, such as the 66 kV windfarm and 220 kV export cable connections.

The Borssele Alpha platform has been handed over during the summer of 2019.

The Borssele Beta platform, which is almost identical to the Alpha platform, has been handed over in July 2020.

HelWin beta Converter Substation

HelWin beta is an O shore High Voltage Direct Current Converter Substation. This means the Alternating Current coming in from the wind farms is converted into a Direct Current in the Converter Substation. This Direct Current is transported via subsea cables and land cables to a Converter station onshore, which will transform the Direct Current back to Alternating Current. This transformation process minimises the energy losses during transport of the energy from the o shore wind farms to the shore. The HelWin beta Substation will be installed in the German part of the North Sea in a water depth of 23 metres and 55 kilometres o the German Coast.

TenneT O shore, the operator of this project, has awarded Siemens the contract to realise the complete O shore Link as the Main Contractor. Siemens has granted Heerema Fabrication Group (HFG) the contract for the Construction of the substation, in which IvO shore & Energy is performing the engineering and design of the Topsides. The Jacket is engineered and designed by HFG Engineering. As the Engineer, IvO shore & Energy will also take care of the Procurement of the non-High Voltage equipment. Iv-Consult, as the Subcontractor of Iv-O shore & Energy, will make the Shop Drawings for HFG. HelWin beta is designed as an unmanned substation, which will normally be remotely operated when no personnel are on board. The HelWin beta Substation will be operated from the control center of the electricity network in Lehrte or from the land station in Büttel. The wind turbines in the connected farms will provide power on 33 kV AC. The turbines are connected to so-called AC transformer substations in the middle of the wind farm, which transform the energy to 155 kV AC. From there, the energy will go to the HelWin beta Transformer Substation. The energy is then rst transformed to 320 kV AC and thereafter, the energy is converted to 320 kV DC.

During the process of converting energy, a lot of heat is released in the transformers and converters. To cool down this equipment, the platform has a large Cooling Water System and an HVAC system, which is connected to the Cooling Water System. The Cooling Water System sends fresh Cooling Water through Circulation Pumps to the equipment. This water will always be on a controlled temperature of 18 to 25°C. The heated water, coming back from the equipment, is cooled by the Seawater Heat Exchangers. In order to do this, the seawater is pumped up, led through the Heat Exchangers and thrown back overboard.

The maximum capacity of HelWin beta is 680 megawatt, this is a su cient amount to provide over 500,000 households with energy. The HelWin beta Substation is designed as a ‘Daughter’ Platform of the ‘Mother’ Substation HelWin alpha.

Borkum Ri grund - O shore Windfarm

Client Dong Energy Denmark

Technical data

Dimensions

Topside (lxwxh): 16 x 35 x 14.5 m (excluding walkway areas, helicopter deck and minor items)

Jacket: 17 x 17m (upper) 30.6 x 30.6m (pile sleeves)

Weight

Topside: 2355 Gross weight

Jacket: 1770 Gross weight

Water Depth 28.9 m

Accommodation

12 persons

Troughput 450 MW

DONG Energy Borkum Ri grund II GmbH holds the consent for OWF Borkum Ri grund 2. The consent presently consists of 56 wind turbines and one o shore substation (OSS), as well as inner park array cables. It is located in the DolWin grid cluster in the German bight, within the German Exclusive Economic Zone. HSM O shore was awarded by DONG to build the platform/substation and Iv-O shore & Energy has been awarded the contract by HSM O shore for the engineering and procurement of a new AC substation. Iv-Consult will produce the shop drawings for both jacket and topside.

With a total capacity of 450MW, Borkum Ri grund 2 will be used to collect and transform the energy generated by the Wind Turbine Generators. Once transformed, these high voltage currents will be exported to the DolWin alpha HVDC Converter Platform via 30-kilometre-long export cables. The o shore wind farm will supply power (free of CO2) to nearly 460,000 households. The platform is expected to be fully commissioned in 2019. Borkum Ri grund 2 (BKR02), is located in the south-eastern part of the North Sea, approximately 38km north o the German island of Borkum.

The o shore substation is constructed as a topside structure supported on a jacket substructure. The jacket substructure consists of a jacket supported by piles.

The substation carries equipment for high-voltage transmission. Besides the high and medium voltage components, the substation is equipped with low voltage systems including SCADA supplying the topside module with electrical power and lighting.

The substation is only manned during service and repair work. All control is carried out from an onshore control station. It has an emergency shelter and welfare facilities for maximum POB 12 persons, which can be used in case of employer’s transport crew vessel is unable to transport crew back to shore.

The substation is accessible by boat and helideck.

The jacket foundation for the DONG Energy’s Borkum Ri grund 2 o shore substation was installed on July 17, 2017. DONG Energy plans to install the topside in the rst quarter of 2018.

DolWin alpha Offshore HVDC Converter Platform

TenneT Offshore GmbH/ABB

Client

ABB

Technical data

Dimensions

Topside (lxwxh): 62 x 43.3 x 40m (excluding Helicopter Deck)

Jacket (lxwxh): 45 x 42 x 44m

Weight

Topside: 11,000 T

Jacket: 4,000 T

Water Depth 27m

Accommodation

TenneT Offshore GmbH is the Electrical Grid Controller of the HVDC Substations in the German sector of the North Sea and the Customer for the Design, Manufacturing and Installation of the HVDC Substations.

Output

ABB Offshore Wind Connections is the Main Contractor for the entire DolWin Project, which consists of the DolWin alpha Offshore HVDC Converter Platform, an onshore transformer substation at Dörpen (Germany) to make the connection with the German electricity grid and all the interconnecting onshore and offshore cables. Heerema Fabrication Group in Zwijndrecht (the Netherlands) was contracted by ABB to design and build the converter platform including its support facilities and they asked Iv-Offshore & Energy to execute the Design.

The DolWin alpha Converter Platform consists of a Jacket with a large Topside and is equipped with an Auxiliary & Emergency Generator, Helideck and a Living Quarter. The Jacket comprises a conventional support structure with six legs, which has a footprint of 24 x 26.4 metres. The legs are supported by six foundation piles driven approximately 55 metres into the bottom of the sea.

The key components of the HVDC Substation are a 155 kilovolt Gas Insulated Switchgear (GIS) for connecting the AC cables to the wind farm, main transformers of 155 kilovolt/320 kilovolt and a 400 kilovolt rated GIS for linking and protecting the main step-up transformers.

The substation and all its supporting systems have a minimum service life of 30 years.

Thornton Bank AC Substation

In response to the EU initiative to increase energy supply from renewable sources, Belgian company C-Power has included an AC Substation, Thornton Bank, in its wind farm development plan. C-Power is responsible for the development and realisation of a farshore wind farm on the Thornton sandbank, which is located approximately 30 kilometres o shore from the Belgian shore. C-Power awarded ABB the contract for the Design, Engineering, Construction and Installation of the electrical infrastructure and the Topside of the AC Substation. ABB has awarded HSM O shore the contract for the Construction and Installation of the Topside. Iv-O shore & Energy executed the Engineering and Design of the Topside steel structure, including the workshop drawings and all their utility systems.

To transfer generated electrical energy in the most economical way, it is necessary to transform the energy to a higher voltage, which has the positive effect of reduced energy leakage.

The Thornton Bank AC Substation will be used to collect, transform and transfer the energy generated by the Wind Turbine Generators (windmills).

The generated energy of the wind farm is collected at the AC Substation. The medium-voltage electrical current is increased in voltage with a transformer and cultivated, such that the electricity can be injected into the Belgian grid without further treatment. The electricity will be transported to shore by two 150 kilovolt high voltage cables of approximately 37 kilometres in length. At the Grid Connection Point in Oostende, the high voltage cables link the wind farm to the Belgian electricity network.

The wind farm comprises 54 Wind Turbine Generators with 5 megawatt to 6 megawatt capacity each. The two transformers on the Topside together have a capacity of 325 megawatt, which is sufficient to provide 600,000 households with renewable energy.

Horns Rev AC transformer station

Horns Rev A is the rst transformer platform ever built and was installed in the rst large-scale o shore wind farm of the world named ‘Horns Rev 1’, which is located in Danish waters in the North Sea. Horns Rev . HSM was awarded the EPC contract for the topside and jacket. Iv-O shore & Energy performed the design and engineering and the topside with a capacity of 150 MW and 3 supporting piles in a water depth of 8 metres.. This Tripod was designed with 5 x 36 kV J-tubes and an independent boat landing structure.