Studies for an electricity cable between Ireland and Britain began in the 1970s, but the engineering problem was always the same: how to push half a gigawatt of power across one of the busiest sea floors in Europe, through a marine environment populated by U-boat wrecks, wind farms, fishing trawls and ferry traffic, and keep it running for thirty years. The answer, when it finally arrived in 2012, was 261 kilometres of HVDC Light cable - 186 of them under the Irish Sea - making landfall at Rush in County Dublin and Barkby Beach in north Wales, from where it runs overland to the converter station at Shotton in Deeside. From the air, it is invisible. On a grid operator's screen it is one of the most consequential pieces of infrastructure on the island of Ireland.
Ireland's electricity grid was, until 2012, a small and largely self-contained system. Self-contained grids are fragile. Lose a major generator and there is no neighbour to lean on. They also waste good wind. Ireland's western Atlantic coast is one of the most resource-rich wind regions on the planet, and there are nights when Irish turbines produce more electricity than the island needs and would rather sell the surplus than curtail it. The East-West Interconnector solved both problems at once. It enhanced security of supply for both Ireland and Britain, opened the door to a coupled wholesale electricity market across the Irish Sea, and let Irish wind power participate in a regional grid. The European Commission classified the link as a priority project under its Trans-European Networks programme.
The route runs from a converter station at Rush North Beach in County Dublin, out across the Irish Sea floor to Barkby Beach in Wales, then over land via Shotton in Deeside, where a second converter station feeds the cable into the British National Grid. Total length 261 kilometres, of which 186 is submarine cable and 75 is buried onshore. The cable carries 500 megawatts at plus-or-minus 200 kilovolts using HVDC Light technology - a voltage-source converter system that was, when commissioned, the first of its kind to run at this voltage class. ABB supplied the cables and the converter stations. The whole project cost roughly 600 million euros, financed by a 300-million-euro loan from the European Investment Bank, a 110-million-euro EU grant, EirGrid equity, and commercial bank lending.
Studies began at the Electricity Supply Board in the 1970s. They were revived in the 1990s as part of a joint study with the UK's National Grid plc, with European Union support. In 2004 the Commission for Energy Regulation, acting on a request from the Irish government, asked the private sector for proposals to build two 500-megawatt merchant cables between Ireland and Wales. A private venture, East West Cable One, was given the contract in 2006 to build two 350-megawatt links, but later that year the Irish government redesignated the project as critical infrastructure and asked the Commission for Energy Regulation to develop it as a regulated 500-megawatt link instead. EirGrid took the work on in 2007 and finished in 2012. The competing private project quietly mothballed its websites by 2016.
On 20 September 2012 the link was inaugurated at Batterstown in County Meath, with the UK Secretary for Energy and Climate Change Ed Davey, Taoiseach Enda Kenny, and European Commissioner for Energy Gunther Oettinger doing the speeches. It has run almost continuously since, with two notable interruptions. On 8 September 2016 a fault occurred during annual maintenance at the County Meath converter station; service partially returned that December at full import capacity but limited export, and full bidirectional capacity took longer still to restore. In March 2022, after a planned three-week shutdown, the interconnector remained below one percent of capacity for an extended period - a reminder that HVDC links of this size are sophisticated, temperamental, and not easily replaced. For most of the time, though, the cable does its quiet work under the Irish Sea, balancing wind against demand on two grids at once.
The submarine portion of the East-West Interconnector runs at approximately 53.5°N along the seabed between Rush, County Dublin and Barkby Beach on Anglesey, then over land to Shotton in Deeside. The mid-channel position is near 53.53°N, 4.83°W. The cable itself is invisible from the air, but the converter stations are landmarks: Rush sits on the County Dublin coast, Shotton on the Dee Estuary near Chester. Best viewed at 5,000-15,000 ft. Nearby aerodromes: Dublin (EIDW) 15 nm west of Rush, Anglesey/Valley (EGOV) on Anglesey near the Welsh landfall, Liverpool (EGGP) 25 nm northeast of Shotton, Hawarden (EGNR) 5 nm west of Shotton. Weather is typically Irish Sea changeable.