avanzate per la sincronizzazione dei PMU Emanuele Ciapessoni*, Diego Cirio*, Giovanni Giannuzzi**, Carlo Sabelli** 2nd International Conference Monitoring of Power System Dynamics Performance – Saint Petersburg, 28-30 Aprile 2008 * CESI RICERCA ** TERNA SpA The development of Wide Area Measurement System (WAMS) technology, combined with Phasor Measurement Unit (PMU) devices, is offering new, valuable solutions for power system analysis, monitoring and control. After the initial applications, limited to off line studies, essentially for modelling and event reconstruction purposes, synchronised phasor measurements have become a reality in the control rooms of utilities worldwide [1]. Operators can thus track system dynamics, in real time and with a degree of accuracy and detail that was not possible with conventional SCADA systems. This allows a deeper and more straightforward understanding of system conditions, and a consistent support in deciding and performing control actions and manoeuvring. Operators can react more promptly and more correctly to disturbances. Synchronised measurements have already proved crucial in critical scenarios. It is worth recalling that a relevant factor in the genesis of the 2003 blackout in Italy was the lack of direct angle measurements at the terminals of the Swiss line that tripped first: on that occasion, worthy time was spent in the unsuccessful attempt to reclose the line, while the manoeuvre was inhibited due to excessive phase angle difference [2]. The paper provides a two-fold focus. The first focus reports the main features and early operational experience of the WAMS realised by TERNA, the Italian system operator, for the synchronised monitoring of the Italian system. TERNA WAMS project also addresses a specific recommendation of the UCTE report on the 2003 blackout [2]. The second focus regards PMU synchronisation. Currently, PMUs rely on GPS for synchronisation. This system has generally proved very reliable and adequate for PMU applications [3]-[7]. On the other hand being a military system, GPS may be not always available. Moreover it may be exposed to failure and to signal alteration by malicious attacks, even if with a very low probability. A redundancy, possibly provided by a civil system, could be an interesting alternative/supplement. The European Union has launched a project (Galileo) to develop a civil Global Navigation Satellite System (GNSS) where, besides high dependability requirements, other services would be provided such as integrity and legal time [8]. CESI RICERCA is involved in a research project (Harrison) [9] co-funded by the Galileo Supervising Authority (GSA) [10], aiming to identify the time synchronization services requirements of future generation of wide area applications and to experiment them in different application fields. The paper presents an outline of the project and reports on the preliminary activity carried out by CESI RICERCA to identify requirements for a new generation of Galileo-synchronised PMUs.