Cabling

Click here to watch a short film about the transformer station.

Click here to watch a short film about laying the land cable.

Electric cabling

The 60 wind turbines of Q7 are connected to each other as well as to the offshore high-voltage substation by means of 22-kV electricity cables. A tube (the J-tube) is attached to the outside of the turbine’s foundation pile, and the electricity cable is then pulled up into the turbine from the sea. To do this, a special ship is used that is able to unwind both 22-kV cables and the 150-kV cables that will be used for the connection to the shore. From this ship, a tracked vehicle is controlled that has been specially designed for this purpose. This vehicle will drive along the sea floor and pick up the unwound cables. It will squirt away the sand with a powerful jet of water and let the cable sink one metre into the sea-floor.

At the high-voltage substation installed in the middle of the wind farm, the voltage is transformed from 22 kV to 150 kV. Otherwise, too much energy would be lost during transport through the cable. A 150-kV export sea cable runs from the station to the shore near Wijk aan Zee. This cable is 28 kilometres long. On the shore, the cable has been pulled under the beach and dunes through 270-metre plastic tubes that have been specially installed for this purpose.

The sea cables

The sea cables comprise three 1-phase cables and a fibre-optic cable, which are bundled into a single, thick cable. Steel wire is wrapped tightly around this thick cable for additional mechanical strength. The 1-phase cables and fibre-optic cable used at sea area are identical to those used onshore, except that these are not bundled into a single, thick cable. Another special aspect is that the 150-kV cable does not consist of separate sections that are linked together, but is actually a single, 28-kilometre cable. As a result, the cable can only be transported by ship.

Mains connection

To transport the green power generated by the turbines to households, a mains connection will be installed. To this end, the 150-kV export cable will be connected to a 150-kV land cable that is connected to the national electricity grid. This 150-kV land cable, which is 7 kilometres long, runs from the dunes at Wijk aan Zee through Beverwijk and Velsen to a high-voltage substation owned by Continuon at the electricity plant in Velsen-Noord. The electricity will then enter the electricity grid.