In the context of a sustainable development the optimal use of the electrical energy will require advanced networks allowing interconnections on very long distances and addressing the storage challenge. These requirements are essentially due to the following reasons: - Electrical energy, contrary to most other kind of energies, must be simultaneously produced and consumed, because it is not possible to store directly large amounts of it. - Electrical energy is generated to a large extent by thermal power plants or by run-of-river stations operating as base load units at nearby constant power.