HKZ platform to be installed despite jacket damage

4C Offshore | Tom Russell
By: 25/03/2022 TenneT
Dutch-German Transmission System Operator TenneT has revealed that the installation of the second offshore transformer platform for the Hollandse Kust (zuid) grid connection project can be carried out as planned.

TenneT has executed investigations on the jacket (substructure) that was damaged in January during storm Corrie by a collision with the adrift vessel Julietta D. According to TenneT, the investigation shows that the damage to the jacket is limited. The damaged parts of the jacket can be repaired at a later stage after topside installation. TenneT expects the Hollandse Kust (zuid) Beta topside to be installed at the end of March or early April.

On Monday 31 January, the freighter Julietta D. was adrift due to storm Corrie in the area where TenneT is building two transformer platforms, Hollandse Kust (zuid) Alpha and Beta. The cargo ship collided with the Beta jacket. No people were working at the platform at that moment.

The persistent stormy weather in February meant that inspections of the damage could not be carried out immediately. In addition to the inspection of visible damage above water, underwater investigations were also carried out to determine any damage to the substructure. This underwater investigation took more time due to relatively high waves and poor visibility. The investigation now shows that the damage is limited to paint damage and a few dents on one of the legs of the platform and damage to one of the four landing platforms for working vessels.

Joris Engelen, TenneT's Platform Project Lead: "When designing and building our jackets, scenarios are taken into account that a ship of limited size may collide with the jacket. After the initial fright of the collision, we set up and implemented an extensive investigation plan in cooperation with the parties involved. The jacket is expected to be in operation for many years. We are therefore relieved that the inspections and the investigations show that we can install the top side of the transformer platform on the jacket safely and as scheduled. After the top side has been installed, the repairs of the damages on the jacket can be carried out." The top side is currently being shipped to its destination in the North Sea. TenneT expects that the top side can be installed at the end of March or beginning of April.

The Hollandse Kust (zuid) Alpha and Beta transformer platforms are part of the offshore grid connection project for the Hollandse Kust (zuid) offshore wind farms. The wind farms,  
Hollandse Kust Zuid 1&2 and Hollandse Kust Zuid 3&4, are being developed by Vattenfall, which secured the rights to the projects with subsidy free bids in March 2018 and July 2019. The sites are owned by Vattenfall (50.5% stake), BASF (24.3% stake), and Allianz (25.2% stake).

The wind farms are located between 18 and 36 kilometres off the Dutch coast, between the Hague and Zandvoort. They will be fitted with 140 units of Siemens Gamesa 11 MW, SG 11.0-200 DD offshore turbines. Once the wind farm is operational, the 140 wind turbines will produce more than 6 TWh of green electricity annually.
Once fully operational, the wind farm will be the largest offshore wind farm in the Dutch waters with 140 wind turbines and a total installed capacity of 1.5 GW. The project is expected to become fully operational in 2023.

For more information on offshore wind farms worldwide, click here.