Major Outage

On 14 February 2024 the East West Interconnector (EWIC) tripped, causing the all-island system frequency to fall to approximately 49.7 Hz. Some 22 seconds later the Moyle Interconnector between Northern Ireland and Scotland also tripped, dragging the system frequency further down to a nadir of 49.582 Hz. The combined loss represented a substantial sudden reduction in import to the all-island system at the time of the trip. The event was reported by EirGrid and SONI in the All-Island Transmission System Performance Report 2024 as the only reportable frequency excursion in Northern Ireland for the year. The interconnector outage was one of a number of short forced outages on EWIC during 2024 that, together with a planned maintenance outage, contributed to the full-year availability of 98.7% (down from 99.1% in 2023). The system operators did not publish a root cause for the dual interconnector trip in the report. Full system frequency was subsequently restored within normal operating limits (49.9–50.1 Hz). The event highlighted the all-island system's sensitivity to simultaneous loss of import infrastructure during periods when interconnector imports represent a high share of demand.