Works on Shetland HVDC link pressing on, first subsea installation set for summer 2022

The Shetland HVDC subsea link project has reached several milestones in recent months with the completion of UXO surveys and the first phase of boulder relocation as well as onshore drilling work.

Set to become the first transmission connection between the Scottish mainland and the island of Shetland, the £660 million project by SSEN Transmission will involve constructing a 260-kilometre subsea cable from Shetland to Noss Head in Caithness.

According to the operator, the HVDC link will support Shetland’s future security of supply and enable the connection of renewable energy generation.

Offshore works

In recent months, NKT has completed the first phase of boulder relocating work along the proposed subsea cable route, clearing a 100 metres wide corridor and removing obstacles. The vessel Seawell was used to relocate the boulders along the proposed cable route.

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Prior to the boulder clearance, a UXO survey was conducted to identify if any unexploded ordnance were in the cable route. The UXO survey was carried out as a standard practice and identified no UXOs within the cable corridor, meaning work could continue as planned. 

Onshore works

A major milestone for the project was reached on land where the horizontal directional drilling (HDD) works to the south of Noss Head lighthouse were completed after three months.

For the HDD works, the drilling scope was executed and the ducts were installed, preparing for when the cable will be pulled through from the seabed through to the transition joint bay where it will tie-in to the land cables which will be connected to the switching station.

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Reflecting on the project achievements so far, SSEN Transmission’s lead project manager Chris Finnigan said: “We’ve made some really excellent progress in recent months with regards to the Shetland HVDC link which allows us to move forwards on connecting Shetland to the mainland and opening up a clean-energy corridor for transporting electricity to and from the islands.”

Next steps

Having reached the abovementioned milestones, the project contractors are now preparing to begin work on the first subsea installations this summer.

The first cable length will be installed by the cable-laying vessel NKT Victoria.

To remind, under the €235 million contract secured in summer 2020, NKT will deliver and install an interconnector to the Shetland HVDC link project.

The order comprises the manufacturing of approximately 2×260 kilometres of 320 kV high-voltage DC on-and-offshore power cables as well as protection of the cables.

The 600 MW Shetland HVDC subsea link project is scheduled to be completed by 2024.

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