Summary
- EirGrid wants large demand facilities to remain connected through defined faults and restore at least 90% of demand rapidly.
- ABB proposes ultracapacitor storage and power conversion to support data centre loads during voltage disturbances.
- Compliance will affect protection, controls, modelling, commissioning, and the commercial terms attached to Irish connections.
ABB has developed an ultracapacitor-based reference architecture for Irish data centres facing proposed fault-ride-through and post-fault recovery requirements, as EirGrid changes the way large electronic loads are expected to behave during transmission disturbances.
The grid-code proposal, known as MPID345, would require affected demand facilities to remain electrically connected during specified faults and recover their active-power consumption after the fault has cleared. EirGrid’s recommendation includes restoration of at least 90% of pre-fault demand within 500 milliseconds once voltage has recovered to 90% of nominal.
Some large data centres currently reduce their grid demand sharply when protection and backup systems respond to a network fault. When several facilities react in the same way, the sudden removal of hundreds of megawatts can create a second disturbance immediately after the original event.
Large electronic loads are no longer passive
EirGrid says more than 2,000MVA of data centre and other new-technology demand has been contracted through its system, with further capacity connected or contracted through SONI and ESB Networks. Data centres and new-technology loads represented around 24% of Ireland’s electrical-energy requirement in 2024 and could reach 30% under the median 2032 scenario.
The effect becomes more pronounced during periods of low national demand. EirGrid recorded an all-island peak of 7,502MW in January 2025 and a minimum of 3,095MW in June 2024, so the same volume of data centre load can represent a much larger share of the system during quieter hours.
Observed faults have produced progressively larger reductions in aggregate data centre consumption as additional facilities have connected. Events that once removed tens of megawatts have begun to affect several hundred megawatts, increasing the challenge faced by network protection and frequency control.
Conventional demand was spread across many different types of equipment and generally remained connected through short disturbances. Modern data centres contain large fleets of UPS systems, variable-speed drives, switch-mode power supplies, protection devices, and automatic transfer controls with similar response characteristics, allowing their behaviour to become synchronised.
ABB’s reference design combines ultracapacitor storage with intelligent power conversion so that the facility can support its internal load during a voltage disturbance while controlling the transition back to normal grid demand. Ultracapacitors are suited to short, high-power events because they respond rapidly and tolerate repeated charge-discharge cycles.
The company models a 50MW data centre using five blocks rated at approximately 8.4MVA. It is a design study rather than a commissioned Irish installation, and an individual facility’s requirements would depend on connection voltage, UPS architecture, protection settings, operating load, and the results of its compliance studies.
Compliance reaches across the electrical system
Installing additional storage will not be enough on its own. Data centres will need validated simulation models, coordinated protection, revised control sequences, testing, and evidence showing how the complete electrical system responds to defined voltage and frequency events.
EirGrid’s process includes root-mean-square and electromagnetic-transient modelling, with studies expected well before energisation. Existing facilities may need to establish whether installed UPS systems, generators, static-transfer switches, and switchgear can comply through revised controls or whether physical modifications will be necessary.
The operating sequence must protect sensitive IT equipment without removing the entire site from the grid at the first sign of a disturbance. Backup power cannot act solely around the internal load if its response creates instability across the wider network.
Controls must distinguish between a fault that the facility is expected to ride through and a condition that genuinely threatens equipment or personnel. Restoring demand too abruptly can create inrush or synchronisation problems, while a slow recovery may breach the proposed code.
Additional storage, converters, modelling, and testing will increase project cost, although failure to comply could delay energisation or require derogations and remedial work. Connection agreements are beginning to define dynamic behaviour as closely as maximum import capacity.
The Commission for Regulation of Utilities has consulted on the grid-code modification and its compliance framework. The final provisions will determine which sites are captured, how quickly the requirements take effect, and the treatment of facilities that are already operating or in construction.
Ireland’s concentration of large electronic demand makes it an early test of a wider European engineering problem. As data centres occupy a larger share of national power systems, their resilience designs will have to account for the facility’s effect on the grid as well as the grid’s effect on the facility.
