1. Reminders of the general problem

EHV (extra-high voltage) transmission and interconnection networks link major production centers with large consumption areas. They also enable power to be exchanged via interconnection lines between countries or large areas belonging to different network operators.

Three major objectives govern the operation of the generation-transport-consumption system, which we will refer to as the power system, rather than the grid, reserving this term for all means of transporting and transforming electricity:

• guarantee operational safety (ensure normal system operation, limit the number of incidents and avoid major incidents, limit the consequences of major incidents)