TenneT files long-term-solution report under 2026 loop-flow derogation, flags need for 2027 derogation

TenneT submitted to ACM on 11 August 2026 the report "Report on methodologies and projects that shall provide a long-term solution to the operational security risks which the derogation granted to TenneT TSO B.V. seeks to address" (ref DEN-MR-NL 26-063, ACM/INT/1072555, case ACM/25/197174). The report is a condition of ACM's 9 December 2025 decision granting TenneT a one-year derogation from the Article 16(8) 70% minimum cross-zonal capacity requirement for loop flows, running 1 January to 31 December 2026. The original reporting deadline of 30 June 2026 was missed; TenneT notified ACM in June 2026 and ACM agreed to later submission. The report documents 2025 loop-flow data on Dutch CNECs (loop flows exceeding the acceptable threshold at least 20% of the time on 28 CNECs, with maxima and frequencies above 2024 levels, partly because restored Meeden phase-shifting transformers freed capacity that loop flows then consumed), lists the remaining enabling methodologies with foreseen implementation dates (Core DA CCM coordinated validation submitted as part of the 3rd amendment of the Core DA CCM with go-live expected in 2026; SOGL Article 76 operational security coordination 2029; CACM Article 35 coordinated redispatching/countertrading 2030; CACM Article 74 RD/CT cost sharing 2030), and projects (grid investments per the Dutch Article 15 action plan, the Bidding Zone Review study published 28 April 2025 with reconfiguration not expected before 2029, and GOPACS). TenneT concludes that because the required methodologies are not yet in place it cannot structurally rely on cross-border remedial actions, and that a derogation remains necessary for 2027, in particular for loop flows exceeding their acceptable level.

The Article 16(8) 70% minimum cross-zonal capacity rule is the central lever for cross-border trade volumes in the Core flow-based day-ahead market. A continuing Dutch derogation means capacity offered on Dutch CNECs stays below the benchmark, constraining cross-zonal exchange and price convergence between the Netherlands and neighbours. TenneT's explicit statement that it will need a further derogation for 2027 signals that the transitional regime — nominally ending 31 December 2025 under the Electricity Regulation — is being extended in practice, and that the structural fixes (coordinated validation, SOGL 76, CACM 35/74, bidding zone reconfiguration) are dated 2026–2030 rather than imminent.

This filing is a compliance artefact with substantive design content: it is effectively TenneT's evidence base for a rolling series of derogations that has run since the 2020 decision (granted 20 December 2020) through 2021–2026. The market-design signal is the mismatch between the regulatory deadline for 70% (ultimately 31 December 2025 via action plans or derogations) and the stated implementation dates of the methodologies that would make 70% operationally feasible on Dutch CNECs: coordinated validation in 2026, SOGL 76 in 2029, CACM 35 and CACM 74 in 2030, bidding zone reconfiguration not before 2029. On TenneT's own account, without those methodologies it cannot structurally rely on cross-border remedial actions, which is the mechanism Article 16(4) presumes. The 2025 data is notable because it shows deterioration rather than convergence: restoring two of three Meeden phase-shifting transformers raised MEE-DIL physical capacity, and loop flows absorbed the increment, so TenneT states there is no indication the need for a derogation will diminish in the near future. Interim mitigation is a voluntary coordinated validation with German and Austrian TSOs since Core DA CCM go-live, which TenneT calls effective but incomplete relative to a Core-wide process. For market participants the practical read-through is continued constrained Dutch cross-zonal capacity in the flow-based day-ahead calculation for 2026 and, on TenneT's stated intent, likely 2027, with the loop-flow root cause attributed to structural congestion in neighbouring zones including Germany. The procedural detail that ACM accepted a late filing without, on this record, any published sanction indicates the reporting condition functions as transparency rather than as a binding lever on derogation continuation.

Article 16(8) and 16(9) of Regulation (EU) 2019/943 (minimum cross-zonal capacity and derogations), Article 16(4) (countertrading and redispatch), Article 15 (action plans), Article 14 (bidding zone review); Regulation (EU) 2015/1222 (CACM) Articles 21, 35, 74; Regulation (EU) 2017/1485 (SOGL) Article 76; ACM derogation decision of 9 December 2025, case ACM/25/197174

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