The specification, design and protection of phase shifting transformers for the enhanced interconnection between Northern Ireland and the Republic of Ireland

NIE is the electricity transmission and distribution company for Northern Ireland and the ESB is the electricity generating, transmission and distribution company for the Republic of Ireland. At present there is a 275 kV AC double circuit interconnection and two standby 110 kV AC interconnections between the NIE and ESB networks. The 110 kV AC interconnections are run normally open and only closed in the event of a system emergency on either network. The 110 kV AC interconnections need to run normally open because it its currently not possible to control the power flows through them and under certain network conditions it is possible that these interconnections could be overloaded. The installation of phase shifting transformers on these lines will control power flows and will enable the 110 kV interconnections to run normally closed and thus enable both NIE and ESB to accrue the benefits of full interconnection.