In a large-scale exercise on 21 June, Transelectrica, together with Hidroelectrica and in collaboration with the Bulgarian transmission operator ESO, successfully tested the scenario for restoring the National Electricity System (SEN) in the event of a major failure. The intervention involved the commissioning of two hydroelectric power plants – Vidraru and Lotru – without external voltage supply, in a controlled simulation of a complete system restoration from blackout.
The test aimed at restarting the SEN through the bottom-up method – from local stand-alone sources and isolated consumers, progressively extending the energy islands and synchronising them into a coherent system. The key point of the operation was the synchronisation of the two energy islands in the Arefu station, followed by the controlled connection to the Bulgarian power system through a pre-configured technical route.
Beyond the technical complexity, the exercise confirms the maturation of the restoration infrastructure and the institutional capacity to manage a coordinated relaunch of the SEWN, including in a regional context. Thus, strategic functionalities such as the start-up of hydropower plants without external supply, the creation of stable micro-systems with local supply capacity, the integration of energy storage in the restoration sequence and the cross-border synchronisation of national energy systems were tested in practice.
The operation involved, in addition to Transelectrica and Hidroelectrica specialists, teams from the distributor DEER and the operator Nova Power & Gas. The test was carried out in safe conditions, with no impact on the current supply, in key locations of the network: Vidraru, Lotru, Arefu, Sibiu Sud, Bradu, Târgoviște and Șotânga.
The event marks a double success: on the one hand, the validation of critical procedures for intervention in case of system failure; on the other hand, the strengthening of regional collaboration as energy resilience and security become strategic priorities for South-East Europe.
Transelectrica thus continues the series of SEN restoration exercises carried out in recent years at CHE Vidraru, Lotru and Iron Gates I. These actions are part of the obligations assumed by Romania under the European Regulation No 2196/2017 on the grid code for emergency situations and restoration and demonstrate the proactivity of the national operator in fulfilling its role within the interconnected European grid.
In a rapidly transforming energy landscape, such tests provide not only confidence in the technical robustness of the system, but also an example of best practice in cross-border operational co-operation.