The NEA Committee on the Safety of Nuclear Installations (CSNI) established a task group to examine Defence in Depth of Electrical Systems and Grid Interaction (DIDELSYS). The DIDELSYS Project, carried out in 2008-2009, made recommendations (see the final report NEA/CSNI/R(2009)10) to strengthen the robustness and defence in depth capabilities of individual NPP onsite electric systems. This was done by systematically evaluating the full range of voltage/frequency transient hazards and planting specific capabilities to cope with these hazards.
In December 2009, the CSNI agreed on a DIDELSYS follow-up activity aimed to
- Identify elements in a methodology on how to periodically carry out a systematic hazard review of possible voltage/frequency transients which could occur from the grid and in NPPs. The reviews would cover the initiators coming from the grid, the generators set and other transients including switching manoeuvres, and their consequences on the electrical distribution systems and powered components inside the plant.
- Identify elements in assessment of the adequacy of design and operational controls to ensure protection against voltage/frequency transients from external/internal electrical systems.
- Initiate a number of sensitivity studies and comparisons of models on individual NPPs for the purposes of identify important issues.