The Pentland Firth sea route runs between the Scottish mainland and the Orkney island of Hoy. This is where, in the summer of 2023, we installed a 33 kV interconnector cable to ensure energy supplies to the Orkney Islands group. The new connection considerably strengthens the local distribution grid.
On behalf of Scottish and Southern Electricity Networks (SSEN), we supplied and installed an interconnector cable between the Scottish mainland and the Orkney Islands group between April and August 2023. A challenging project, both due to the client’s tight timeline and the difficult soil conditions and strong currents that characterise the strait.
We took on the installation and protection of the cable and outsourced the fabrication and transport to cable manufacturer Ningbo Orient Cable.
A fleet at top speed
Cable installation vessel Connector installed the 43 km export cable in spring and summer 2023. We also deployed our cable trencher Swordfish for the first time, controlled from the offshore support vessel Symphony. The trencher proved an immediate success and completed its scope faster than expected. Where the cable didn’t require burying or where this was not possible due to the hardness of the seabed, the multi-purpose vessel Adhémar de Saint-Venant placed rock bags all around the cable to stabilise it against the current.
Planning geared to tidal current
During the installation works, we paid close attention to the tidal current, making sure we could install the cable in the strait when the current was at its weakest. When the current picked up again, we continued the works in the shelter of the bay.
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