Approval of SONI’s proposal on Article 39(3) of establishing guidelines on electricity transmission system operation

Article 39(3) of the System Operation Guideline (SOGL) relates to the requirements on minimum inertia. This update is intended for stakeholders affected by European Network Codes.

Inertia can be defined as energy stored in large rotating generators. This stored energy can be particularly valuable when a large power plant fails, as it can temporarily make up for the power lost from the failed generator. Therefore, the requirements of minimum inertia are relevant for frequency stability at the synchronous area level.

SONI and Eirgrid jointly submitted a proposal on Article 39(3) to the regulatory authorities (RAs) of Northern Ireland (Utility Regulator) and Ireland (Commission for Regulation of Utilities (CRU)) on 13 September 2019.

A review was subsequently undertaken by the RAs, which determined that the studies provided concerning the establishment of the minimum required level of inertia were not sufficiently up to date. After several discussions on the topic of this decision letter between the TSOs and the RAs, the TSOs resubmitted a proposal on 16 June 2022.

Pursuant to Article 6(7) of the SOGL, we have closely cooperated and coordinated with CRU to reach an agreement on resubmitted proposal.