WIND FARM DESIGN

Offshore farm grid connection


Introduction
        Grid connection of offshore wind parks is not a major technical problem per se, in the sense that the technologies which are involved are well known. Optimising these technologies for remote offshore sites will be important, however, to ensure reasonable economics.
        Below, some considerations about the grid connection are mentioned:


Cabling
        Undersea cabling connecting offshore parks to the main electrical grid is a well known technology. Undersea cables will have to be buried in order to reduce the risk of damage due to fishing equipment, anchors, etc. If bottom conditions permit, it will be most economic to wash cables into the seabed (using high pressure water jets) rather than digging or ploughing cables into the bottom of the sea.


Voltages
        Inside the large 120-150 MW wind parks being planned in Denmark, it is likely that 30-33 kV connections will be used. In the middle of each park there will probably be a platform with a 30 to 150 kV transformer station, plus possibly a number of service facilities. Connection to the mainland will be done using 150 kV connections.


Reactive power, HVDC
The undersea cables will have a high electrical capacitance, which may be useful to supply reactive power to the parks. It may be optimal to have some form of variable reactive power compensation built into the system, depending on the precise grid configuration. If the distance to the main grid is considerable, an interesting alternative could be to connect the parks to the mainland using high voltage direct current connections (HVDC).
        Reactive Power is related to phase-shifting of alternating current, which makes it more difficult to transport usable energy through the electrical grid.





Video frames
- Electrical transmission, Horns Rev-DK: general notes on map and figure
- Topology of grid connection: general for offshore grid connection
- Shore connection options: AC, transformer or no, DC
- Power collection and transmission: components list and general notes
- Installation of cables: explanation with photos
- Offshore wind farm electrical systems: electrical data of offshore wind farms
- Limiting factors for AC transmission: notes
- Allowable current AC cables: notes
- Transformer platform, Horns Rev-DK (A): installation
- Transformer platform, Horns Rev-DK (B): components of platform