Summary
- MPID 345 became effective on 27 October 2026 after the regulator’s 22 September decision.
- Requirements concern transmission-connected demand facilities generally, not data centres alone.
- EirGrid’s approved compliance and derogation framework addresses existing loads requiring further work.
Ireland’s Grid Code modification MPID 345 became effective on 27 October 2026, introducing new technical requirements for transmission-connected demand facilities to remain connected during short disturbances on the electricity system. Data centres are among the affected classes of large demand, but the measure applies to relevant transmission-connected facilities generally rather than to data centres alone.
The Commission for Regulation of Utilities approved the modification on 22 September, together with an amended compliance and derogation framework proposed by EirGrid. The regulator specified implementation five weeks after its decision; the transmission system operator’s published modification register confirms 27 October as the effective date.
The change addresses a power-system risk created when many large electricity users disconnect together during a disturbance. A transmission fault can produce a short voltage dip across an extensive area. If facilities protect their equipment by immediately shedding large quantities of demand, the resulting sudden imbalance can create additional difficulties for maintaining system frequency and stability.
Fault ride-through and recovery
Fault ride-through describes the ability of connected equipment to withstand specified, temporary departures from normal grid voltage without immediately disconnecting. A related requirement concerns the rate of change of frequency, while post-fault active power recovery deals with how demand returns once system conditions have improved.
Demand that remains connected during a voltage dip must also recover in a manner compatible with transmission-system operation. MPID 345 covers both the disturbance and the behaviour of active power afterwards, alongside the rate of change of frequency. Passing one part of that assessment does not establish compliance with every relevant requirement.
Electricity networks depend on generation and demand remaining in close balance. A rapid loss of a substantial block of demand can be problematic in its own right, even though loss of load is commonly associated with reduced consumption rather than extra demand. The risk arises from the scale and speed of the change, and the reaction of power-system controls and generation assets.
Data-centre installations contain electrical systems whose response may depend on the upstream grid connection, transformers, uninterruptible power supplies, protection settings and the interfaces between utility and facility equipment. Those arrangements vary considerably between sites. The new rules do not establish that all data centres behave alike or that every site must use an identical modification.
Operators must distinguish the performance of the facility at the grid connection from the continuity of supply delivered to individual IT racks. Backup systems can protect customer equipment during utility disturbances, but a facility’s net effect on transmission demand remains relevant to the system operator. A design that maintains server availability may still need engineering assessment against the Grid Code.
Compliance framework for existing facilities
The CRU also approved a framework intended to provide a route to compliance for facilities already connected to the network. Existing equipment may not have been installed against the newly specified performance criteria, and demonstrating compliance can require modelling, technical studies, operational information or plant changes.
The framework includes a derogation process for relevant facilities while longer-term solutions are developed. A derogation should not be described as a general exemption that removes all responsibilities; its significance depends on the particular application, conditions and route approved under the framework. Operators need to establish which parts of their equipment and connection arrangements are in scope.
The CRU’s September decision followed consultation and further requests for representations earlier in 2026. Submissions raised technical and commercial concerns, including the practicality of alternative solutions and the way the system would operate while not every existing connection could satisfy new requirements immediately.
Existing facilities may need time to demonstrate the performance required by the approved technical framework. The September consultation and subsequent decision provided a compliance and derogation process rather than evidence that every affected connection had already completed engineering changes by 27 October. Obligations are effective even though individual compliance arrangements may differ.
Distribution-connected facilities are a separate matter. The approval relates to the transmission Grid Code, and it would be inaccurate to imply that every data centre connected through a distribution network has automatically acquired precisely the same obligations under this decision. Related distribution-code initiatives would require their own formal treatment.
The regulator expects continuing information from EirGrid after the modification takes effect, including quarterly reporting on its implementation. That monitoring can clarify the progress of engineering assessments and any derogations without implying that every site has identical electrical architecture or faces the same remedial work.
Transmission-connected demand operators now face an effective Grid Code requirement to tolerate specified disturbances and recover their active power appropriately. The approved framework sets out a route for existing facilities to demonstrate compliance or seek relief in defined circumstances. Requirements for distribution-connected facilities must be established under the applicable separate code provisions.
