Red Eléctrica de España, S.A. (REE) aim is to ensure the correct operation of the Spanish Power System carrying out two main activities: The operation of the Spanish electrical power system and the transport on the high voltage power network. As SO, REE guarantees the continuity and security of the power supply and the balance between generation and demand. To achieve its goals as SO, REE has developed an information system known as ‘Sistema de Información del Operador del Sistema (e·sios)’, specially designed to run all the necessary processes to ensure an economic and reliable exploitation of the Spanish Power System in real time.