In accordance with Art.8 of the Quality of Service Regulation (RQS), some exceptional events can be excluded from the evaluation of service continuity standards. Exceptional events should cumulatively meet the following characteristics:
Low probability of occurrence;
Result in a significant reduction in the quality of service;
It is not economically reasonable for the National Transmission System Operator (TSO) to avoid all of its consequences;
TSO is not responsible for the event or its consequences.
In some cases, when properly justified and the TSO is not responsible for the occurrence
of the events, the TSO can also request the exceptional classification,
even if the events do not totally comply with the necessary conditions
to be considered as a high impact incident.