The topside for the offshore transformer station for the 759MW Hollandse Kust (north) offshore wind project has been successfully placed on the jacket, TenneT has announced.
With the help of the installation vessel Orion, this new milestone took place 18.5 kilometres off the coast of Egmond aan Zee.
From next year, TenneT will bring sustainable wind energy ashore via this ‘socket at sea’.
After a brief stopover in the port of IJmuiden, the topside arrived at its destination from Hoboken, Antwerp, Belgium, on Monday.
Offshore platform project manager on behalf of TenneT Guus Siteur said: “We had to wait until the installation vessel Orion was available and weather and tidal conditions offered us a favourable time window.”
The undercarriage (jacket) has been firmly anchored on the seabed since November last year.
According to Siteur, placing the topside went relatively quickly.
He said: “A large crane on the Orion lifted the 3,500-tonne steel structure off the floating pontoon.
“Both the jacket and the topside are attached to so-called cones.
“These can be compared to ice cream cones that fit together perfectly.
“This allows you to lower the topside in exactly the right place.”
Later, a jack-up barge (lifting vessel) was placed next to the socket at sea.
Siteur added: “Once this has extended its legs and the ship is suspended above the waves like a platform, a walkway is suspended between the ship and the platform.
“Some 50 people will stay on the ship for the next few months. They will weld the topside to the jacket and take care of commissioning the installation.”
Next month, TenneT will also test the fibre-optic connection, which has been laid together with the sea cables.It can then be commissioned to control the unmanned socket at sea.
Siteur said: “With this, everything will soon be controlled from our operations centre in Arnhem.
“In addition to the transformers that bring the voltage level from 66 kilovolts to 220 kilovolts for efficient transmission, there are also 130 kilometres of cable in the topside to connect all systems.”