The Moyle HVDC Interconnector: project considerations, design and implementation

The Moyle Interconnector will transmit power between the electricity systems in Ireland and Great Britain from the end of 2001. It will provide Northern Ireland with an important new source of electricity supply, promoting competition in the emerging markets in Northern Ireland and the Republic of Ireland and enhancing security and quality of supply. The overall project costs are approximately 150 million. The project is sponsored with a contribution of 52.5 million by the European Regional Development Fund. The implementation of the Moyle Interconnector involves the construction of 64 km of 275 kV AC overhead line in Scotland, HVDC converter stations in Scotland and Northern Ireland, underground DC cables from each station to the coast and the installation and protection of 2×55 km of subsea DC cable. The elements that make up the Moyle Interconnector project are required to be technically feasible, reliable and economically viable. They also require to be designed, constructed and operated taking into account environmental considerations. As imports over the interconnection will represent a significant proportion of the Northern Ireland system demand, the design of the link must ensure that quality of supply experienced by customers will be at least as good with the interconnection in service as prior to its introduction. A main criterion influencing the Interconnector design was that its performance in reliability and availability terms should be no worse than that of an equivalent sized onshore modern generating unit. The implementation of the Moyle Interconnector requires it to be economically viable with a balance between mitigation of any potential environmental impact in conjunction with the requirements of statutory bodies and a technical solution that delivers the requisite reliability and availability.