On May 28, 2025, the slack node of the Nordic synchronous area used for the Flow-based capacity calculation was changed from the bidding zone DK2 (Hovegaard) to SE2.
Operational background: on the energy delivery day May 28, starting at 06:30 a busbar in station Hovegaard was deenergized as a planned outage. Normally, this station is the most meshed station containing a PV node in the grid model. Thus, the node representing this station is generally selected as the slack generator of the Nordic synchronous area. Due to this planned outage, the ‘slack generator’ is disconnected after 06:00.
Operational procedure: the slack node is not a fixed node in the power system. Instead, it is dynamically selected as the most meshed node among all PV/Pθ nodes at the highest possible voltage level. This is to prevent that – in case of a major outage – no slack node would be available for the remainder of the grid and the FB CC would fail. From the operational perspective, the slack node selection is an automated internal step within the normal FB CC computational process.
New slack node: following the operational procedure, the new slack happened to be the most meshed node located in SE2 (previously it has been Hovegaard in DK2). This change followed the established automated procedure used within the FB CC computation process.
Market Impact: the slack node change has no impact on market coupling results.