Completes inter array grid cable installation works of the Nordsee One Offshore Wind Farm


The ISV/SOV vessel 'Siem Moxie' is working as part of a 'Siem Duo' in cable installation works on the Nordsee One Offshore Wind Farm (OWF). Three weeks ahead of schedule, the inter-array cables for the wind farm had been installed, as well as the foundations and the offshore substation for the 54 wind turbines. ​

The 'Siem Duo' is consisting of the Cable Lay Vessel (CLV) Siem Aimery and the Service Operation Vessel (SOV)/Installation Support Vessel (ISV) Siem Moxie. The Siem Moxie is assisting the CLV for the submarine cable pull-in, termination and testing activities. The vessel's active motion-compensated “Walk to Work” (W2W) gangway is used to safely transfer personnel to and from the individual foundations. The ISV Siem Moxie had already established a track record of over 30,000 successfully executed personnel transfers since delivery in April 2014, proving its capability as one the most advanced, safe and efficient service operations vessels available in the market.

On 6 September 2016, Siem Offshore Contractors announced that all 70 kilometres of inter array grid cables on the Nordsee One Offshore Wind Farm in the German Bight of the North Sea have now been installed, terminated, trenched and tested three weeks ahead of schedule.

All 59 cables were successfully installed using the 'Siem Duo' vessels. These were supported by a further in-house Multi-Purpose Vessel (MPV) Siddis Mariner, which provided subsea support for the installation of cable protection systems and concrete mattresses. The Siem Duo demonstrated their advanced weather operability during this project and particularly with gangway access being completed in up to significant wave heights of 3m from the (ISV) Siem Moxie.

The CLV Siem Aimery loaded in excess of 70 km of aluminium core submarine composite cables directly into its two turntables in addition to cable protection systems, which were loaded into a dedicated under-deck storage compartment.

In parallel the ISV Siem Moxie assisted the CLV Siem Aimery with the cable pull-in, termination and testing activities deploying its offshore support units (OSU) equipped with generators, pull-in winches, tools and equipment for personnel life support at the individual offshore work sites. The OSUs were transferred using the vessel 3D motion-compensated crane, while the vessel active motion-compensated “Walk to Work” (W2W) gangway was used to facilitate more than 8,000 personnel transfers to and from the individual foundations and offshore substation.

Mr. Regis Rougier, Managing Director of Siem Offshore Contractors stated:

“It is a pleasure to confirm the successful completion of our first project utilising the “Siem Duo”. Both the crews of the Siem Aimery and Siem Moxie have made us proud by consistently delivering high quality execution while concluding the project ahead of schedule! We are looking forward to the next challenge for our teams and of course the next project for our vessels.”

Harald Poppinga, Project Manager for Siem Offshore Contractors added:

“It has been a pleasure to be part of this milestone achievement - envisioned in 2013 and delivered in 2016!”

Siem Offshore Contractors was awarded the engineering, procurement, installation and commissioning (EPIC) contract for the IAG cable system of the Nordsee One OWF in 2014. The 54 WTGs of the Nordsee One project are located 40km north of the island of Juist in water depths of up to 34 metres.

SIEM Offshore Contractors supplied, installed, terminated and tested the submarine cables and associated accessories for Nordsee One wind farm.

The cables have a diameter of up to 160 mm and a weight of up to 36 kg/m. During the installation and operational phase of the project, a layer of steel armor wires protects the high-performance electricity conductors and fiber-optics. The cables were laid and buried using the new purpose-built cable installation vessel, the Siem Aimery. The vessel was supported by the Siem Moxie, which facilitated the transfer of personnel to the structures via a walk-to-work-system.

Pierre Lestienne, Managing Director (CFO) of Nordsee One GmbH, said:

“Looking ahead, in the upcoming weeks the export cables will be installed by the grid operator. We will then commission all of the electrical systems in preparation for the connection of the wind turbines, which we plan to begin installing in early 2017, when the weather conditions allow,”

Once completed, Nordsee One wind farm will consist of 54 wind turbines with an overall installed capacity of 332 MW. The wind farm is owned by Northland Power Inc. (85%) and Innogy SE (15%), a subsidiary of RWE.

Update 2018: The Siem Duo has been acquired by Subsea7, and the vessels changed names to Seaway Aimery and Seaway Moxie.

ULSTEIN SOV references

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