THE NEW GREENLINK 500 MW INTERCONNECTOR

European countries are committed to decarbonising power generation with clear goals over the coming decades. As a consequence, an energy transition from fossil fuel generation to renewable energy sources is required. This will influence electrical transmission systems which will need to develop and adapt to changes that new renewable energy sources bring. Electricity grids can accommodate these changes more easily if they are connected to other grids, thus allowing for power exchange and stability support during operation. The Great Britain and Ireland electricity grids are classed as islanded power systems with few interconnections. Interconnectors are high-voltage cables or transmission lines used to connect the electricity grids of different regions or countries. They are an asset for increasing energy security and reliability, stabilizing the price of electricity and supporting integration of renewable energy sources. Interconnectors are used to balance supply and demand by transferring excess renewable energy from one country to another. Ireland had only two interconnectors in operations until beginning of 2025: Moyle Interconnector, between Scotland and Northern Ireland, East-West Interconnector, between England and Republic of Ireland. An additional two interconnectors are being established. The Celtic Interconnector, between the southern coast of Republic of Ireland and the north-west coast of France, is expected to begin operation in 2026 and the Greenlink Interconnector, between the eastern coast of Republic of Ireland and south-west Wales, which went into operation in 2025. The Greenlink Interconnector is a subsea and underground electricity interconnector cable with a nominal capacity of 500 MW that connects the electricity grids of Ireland and Great Britain. It consists of two converter stations – one located near Great Island substation in County Wexford and the other near Pembroke substation in Pembrokeshire – connected by the High Voltage Direct Current (HVDC) cables under the Irish Sea. The total length of the cable is 200 km, with 160 km being installed under the sea. The HVDC link is configured as a symmetrical monopole operating at a voltage of ±320 kV d.c. The Greenlink Interconnector will provide a bi-directional power supply, depending on the supply and demand in each country and will double the interconnection capacity between Ireland and Great Britain and increase the security of supply for consumers, as well as further the integration of low-carbon energy sources. Greenlink Interconnector will contribute to the economic and environmental development of both Ireland and Great Britain. This paper outlines the methodology and technologies used for project design, as well as the significance of the project.