The All NEMO Committee, the body responsible for overseeing EU coupled power markets, recently published a report (click here) on a partial decoupling incident involving the Intraday Auction (IDA) in the Single Intraday Coupling (SIDC) market.
Decoupling refers to the process where parts of the coupled EU electricity market are temporarily separated from the coupled market operation. This occurs when an underlying issue prevents one or more parties such as Transmission System Operators (TSOs) or the Nominated Electricity Market Operators (NEMOs) from participating in the continuous or auction market within the required timeframe. The most recent case involved the latter. Full Decoupling occurs when the entire market coupling process is stopped or cancelled, in which case all participants revert to local market-only trading. Partial decoupling occurs when only some market areas are separated, while the rest of the market remains coupled. The incident in question involved the partial decoupling of the first intraday auction (i.e. IDA1).
The incident originated in Spain and involved Red Eléctrica, the Spanish TSO, and OMIE, the power exchange (and NEMO) for the Iberian power market. While classified as a partial decoupling, it implicated a broad cross-section of the EU coupled market (see below). The incident occurred on 14 October 2025 when the results for the Single Day-Ahead Coupling (SDAC) auction for delivery day 15 October 2025 were delayed until 13:12 (the hard deadline is set for 12:42, hence a 30 minute delay). This delay reduced the time available for the TSO to execute its internal post–day ahead, pre–intraday security analysis (these are checks to ensure the physical flows are feasible on the grid without causing grid stability issues) before the IDA1 deadline at 15:00. Because of this, the TSO finished its security analysis four minutes after the deadline. Red Eléctrica informed OMIE in advance of the deadline that its security analysis would not be completed on time.
OMIE was not able to participate in IDA1 without the required security analysis data from the TSO. At 14:59 on 14 October, OMIE informed all the other NEMOs that due to the lack of necessary information, it could not participate in the IDA1 auction and an Automatic Partial Decoupling was triggered. Only two market areas remained coupled, namely Italy-Greece i.e. GME (Italy) and HENEX (Greece). The report does not provide any explanation as to what caused the delay in the publication of the DA auction results.
The report (see page eight) offers relatively little detail in the way of lessons learnt, saying only that “NEMOs and TSOs are exploring potential fallback measures to mitigate similar situations”. Red Eléctrica was in the news lately for its involvement in the Iberian power market blackout that occurred in April this year (see here).
While decoupling is generally of interest to front office and market operations teams, such incidents may also carry implications for compliance. The reversion to local market trading may drive sudden and precipitous changes in market dynamics which may have knock-on effects for algorithms active in these (and closely related) markets such as the continuously traded SIDC market. As such, the timing of such incidents represents a potential window of interest for compliance and surveillance officers.