Ireland’s first energy link to EU shaping up with ‘steady progress’ on cable routes for French interconnection

A one-year construction milestone has been reached at a subsea cable interconnection project between Ireland and France, known as Celtic Interconnector, only two years since the signing of the engineering, procurement, and construction (EPC) contracts in Paris. This project, which aims to enable the exchange of electricity between the two countries, has made inroads in east Cork and France.

The Celtic Interconnector, being developed by the Irish transmission system operator (TSO) EirGrid and its French counterpart Réseau de Transport d’Electricité (RTE), is said to be coming along thanks to progress made this year, with substantial portions of underground cable now in place and the next stage of the cabling process, joining cables, underway.

According to EirGrid, “vast ground works” were done at the converter station site at Ballyadam, near Carrigtwohill, enabling the steel works assembly to begin. The converter station building is now being constructed as Siemens Energy and contractors continue with main civil works at the site, with the steelwork for the converter building perceived to be advancing apace.

Upon completion, the converter station will transform high-voltage direct current (HVDC) to alternating current (AC) and vice versa, allowing the flow of electricity exchange between the Irish and French grids. Designed to enable the exchange of 700 MW of electricity between Ireland and France, the Celtic Interconnector will move the electricity across 575 kilometers (km), with 500 km of the cable running under the sea, to supply electricity to 450,000 homes.

EirGrid claims that teams continue to make “steady progress” on the cable routes, with trenching and ducting on the 400 kV AC cable route now complete as road reinstatement continues, in cooperation with Cork County Council. Previously, Greece’s Asso.subsea disclosed that it would pool resources with Nexans to perform subsea burial operations for Ireland’s first power connection with continental Europe.

The trenching and ducting continue on the 320 kV DC main route sections, the N25, and local roads. In addition, cable jointing is ongoing on the 400 kV AC main route sections. However, archaeological investigations are complete on the beach at Claycastle, the landfall location, with outcomes awaited.

“With significant portions of underground cable now in place, the next stage of the cabling process, joining cables, is now taking place. This work is taking place in the joint bays which are placed along the route,” explained the Irish TSO.

EirGrid has confirmed that work is ongoing on the network connection point at Gogganstown 400 kV substation, adjacent to the Knockraha 220 kV substation, where the 400 kV HVAC electrical supply from the interconnector will be converted down to 220 kV and connect to the transmission grid. The marine operations in Irish waters are finished for this year.

Michael Mahon, Chief Infrastructure Officer at EirGrid, commented: “This milestone is a testament to the collaboration of all involved and is only made possible by the dedication of our workforce, contractors and subcontractors and the communities of east Cork who continue to facilitate these works.

“Their support and cooperation have been invaluable, and we will continue to engage with them as we progress toward completing this vital infrastructure. As we continue into the next phases of construction, our team remains committed to safe and efficient delivery of this strategic project and look forward to achieving new milestones together in 2025.”

While celebrating the one-year construction milestone, EirGrid teams and project partners welcomed the Ambassador of France in Ireland, Céline Place, to the converter station site in Ballyadam in November 2024. At RTE’s end, the landfall works at Cléder and Saint Pol-de-Léon were wrapped up before summer, enabling the focus to be on the installation of the transition joint bay until the end of the year.

The construction of the trenching and ducting works is also progressing through several municipalities. The ‘Azénor’ micro tunnel boring machine has completed works under the Elorn River and the railway line between Brest and Paris.

The estimated number of work hours dedicated to the project is 816,000 by Celtic Interconnector Designated Activity Company (CIDAC). As part of EirGrid’s role, it manages 7,500 km of electricity circuits, including overhead power line and underground cables.

The activities planned for 2025 encompass the start of offshore marine cable installation, the installation and jointing of HVAC and HVDC land cables, and the completion of converter station buildings. The work for 2026 covers the completion of offshore marine cable installation, submarine cable protection campaigns, commissioning tests, interconnector system tests, and the beginning of the trial operation period.

The Celtic Interconnector project is envisioned to create an electrical interconnection between Ireland and France to allow the exchange of electricity between the two countries, linking the existing electricity substation in Knockraha, east Cork, to the substation in La Martyre in Finistère, France.

As a result, the project is expected to contribute to a more secure and sustainable electricity supply by providing Ireland’s only direct energy connection to a European Union (EU) member state. This subsea link, which got a €530.7 million slice of Connecting Europe Facility (CEF) funding in 2019, is slated to be completed in 2026.