In 2010, a European Memorandum of Understanding – the North Sea Countries Offshore Grid Initiative (NSCOGI) – was signed by 9 countries, agreeing a programme of massive offshore wind development around the North & Baltic Seas and UK coastline. With several countries in Europe fully embracing the concept of offshore wind power any suggestion that this is just a passing phase in renewable energy development is blown right out the water.
INCREASING DEMAND FOR EXPERTISE
For those with early and uncommon experience in this domain, it’s a busy time. With Tractebel Engineering’s knowledge of every facet of electrical Transmission & Distribution (T&D) and ability to provide the innovative solutions needed in offshore wind park connection, our T&D team is right in the middle of the action! Proven on BELWIND (165 MW, 50 km off the Belgian coast), our offshore expertise covers the full electrical design for offshore wind parks; from the foot of the wind turbine generators (WTGs) to the connection with the TSO or onshore power grid. Central to this is the optimisation of the electrical design of the offshore substation(s). Read more
A WINNING TEAM!
Tractebel Engineering is involved in Germany via the same consortium that first joined forces on BELWIND. Read more
4 GOOD REASONS
In terms of offshore wind connection technology, Tractebel Engineering is more than ready to go. But developers face other limitations…
- BELWIND platform – photo Vanoordmennomulder
- BELWIND - Transport of the offshore substation platform – photo Bart Verbeeck
- BELWIND - Foundation poles of the wind turbines – photo Bart Verbeeck
- BELWIND - Offshore platform under construction – photo Bart Verbeeck
- BELWIND – Platform transport preparation – photo Bart Verbeeck
- BELWIND - Platform transport preparation-2 – photo Bart Verbeeck
- BELWIND – Lowering the substation onto the transport vessel – photo Bart Verbeeck
- BELWIND - Laying of the grid connection cable – photo CG Holdings Belgium
OFFSHORE WIND CONNECTIVITY → The WTGs generate power at 33kV →Generated power is sent to an offshore substation via a network of MV marine cables → The offshore substation collects this power and transforms it to a HV at 150 kV → This is exported via HVAC cable to the first point of connection (either an offshore DC converter station or an onshore substation) with the TSO/Grid.
Out to sea!
An unmanned offshore substation is a complex, active system incorporating: HV switchgear, auxiliary power, shunt reactors and many other systems and electrical components. This calls for a SCADA (Supervisory Control and Data Acquisition) communication/monitoring/control link to an onshore control. Offshore, a new and important SCADA function is Megavar (Mvar) control; a key concern for operators who must maintain a TSO specified Mvar/MW balance in the onshore transmission. The integration of SCADA systems and installation of automated shunt reactors to help regulate Mvar flow on the BELWIND project is a good example of how our T&D expertise is being adapted to meet new offshore needs.
Wind offshore in Germany
In Germany, the (expensive) costs of HVAC export cable between platform and shore are borne by the TSOs. As of 2015, legislation changes will see this cost being carried by the developers – so there’s a rush on German projects to avoid this investment. Tractebel Engineering T&D, contracted to Crompton Greaves – CG Power Systems Belgium; leading manufacturers of power and distribution transformers, have begun work on 2 new German projects: connecting AMRUMBANK WEST (E.On Climate Renewables) and BUTENDIEK (wpd AG.) to TSO – TenneT.
Both wind parks, 288 MW with 80 WTGs (Seimans 3.6 MW), will have 1 offshore substation and 2 HVAC export cables. TenneT also plans to install a DC plug offshore to convert the AC power from the substations to DC power, allowing less costly HVDC cable to be used for the transmission to shore. Working on these projects, utilising different technical concepts, will add meaningfully to our growing expertise in this field. Meanwhile, getting started, our T&D team is focussed on defining the best technical solutions available to the clients and the process of permitting and project approvals.
“The offshore partnership between CG Power Systems and Tractebel Engineering is based on transparent communication and performance. In any renewable energy project, time = money, lots of money! We succeeded in completing this project faster than the contractual planning, fully realizing the design, the build and the testing of the offshore High Voltage substation in less than one year. Thanks to a complex and exhaustive test plan on land, we avoided many expensive and cumbersome offshore interventions. In the offshore market Belwind is widely recognized as a great achievement.” Etienne Lemaire, Engineering Manager – CG Holdings Belgium NV – Systems Division
NEVER CHANGE A WINNING TEAM!
The same consortium that joined forces on BELWIND wind farm in Belgium: a framework constructor, Fabricom (GDF SUEZ) (installation) and Crompton Greaves – CG Power Systems Belgium (design, engineering and supply) went on to win 2 more contracts for wind farms in Germany: connecting AMRUMBANK WEST (E.On Climate Renewables) and BUTENDIEK (wpd AG.) to TSO – TenneT.
As on BELWIND, Tractebel Engineering are contracted to CG Power Systems Belgium; leading manufacturers of power and distribution transformers, with a reputation for using the most advanced technology and the highest production standards. Tractebel Engineering’s scope covers the systemic and detailed design, testing and commissioning of the transmission installations. As many technical issues were raised in the project contract negotiations, our experts also played a key role in convincing the clients that the consortium could provide the right solutions.
WIND OFFSHORE IS NOT ABOUT TO DIE DOWN
The increased activity and investment in offshore wind power in the last 10 years clearly illustrates that this is not just a passing phase in renewable energy development:
► Wind turbine generator (WTG) manufacturers have focused on developing larger, more robust wind turbines (up to and exceeding 5 MW) to bring down costs through better economies of scale.
► With greater power potential, large offshore wind farms are being seen as a real alternative for nuclear power. Fears of rising costs and the political stability of oil supplies are an added motivation.
► Industry players are also focused on reducing costs of installation, operation and maintenance through technical innovation and investments in vessels, foundations and port facilities.
► Transmission System Operators (TSOs) are taking long-term steps to extend and reinforce their national power grids to accommodate future offshore wind power projects (although the permitting needed to do this can take years to progress, which is a challenge in the interim). Europe’s TSOs are also planning to standardise their TSO grid connection requirements (Grid Codes) which is a positive for developers.
OFFSHORE CHALLENGES TO CONSIDER
The need for auxiliary power ► Wind turbine generators (WTGs) need power to send warning signals to passing ships or aircraft. The nacelle (the house-size hub at the base of the blades) has to move at least once a day to avoid weight-induced mechanical damage. Without wind, this relies on auxiliary power. Offshore substations also use auxiliary power for services like H-VAC (keeping equipment at ambient temperature), communication and lighting. In normal operation, this is created by auxiliary transformers. In an emergency (no connection to the TSO grid), diesel generators on the platforms, or flown in by helicopter, must take over.
Cabling constraints ► Laying or replacing long lengths of undersea cable calls for special vessels, is expensive and is only possible in good weather (a short season in northern seas!). The large export HVAC cable, currently only supplied by a limited number of manufacturers, has to be custom-made according to the unique requirements of each wind farm – the number and MW size of the WTGs and the distance to shore.
Grid connections ► Every TSO has their own grid code – and when you connect a large wind farm to a grid you have to meet certain technical requirements which differ for each TSO. For now, there’s no such thing as a standard offshore substation design. In addition, most European grids still have to be reinforced to accept the additional power from wind offshore projects. The permitting for this could still take years to progress – limiting wind offshore projects in the interim.