On-line dynamic security assessment to mitigate the risk of blackout in the Italian power system

This paper provides a comprehensive survey of the major initiatives and research projects recently carried out by the Italian system operator, Cesi Ricerca, and Universities on power system monitoring, defense, and security assessment. The technological and methodological features of an advanced wide area measurement system (WAMS) are described and the main aspects of an adaptive system for event-based automatic load shedding are presented. Then preventive and corrective security assessment, with particular emphasis to dynamic security assessment-DSA, is introduced. Results from an EU project, where the Italian power system served as a test site for on-line experimentation, are reported. Considering the need for very fast assessment by stability indices, a complementary approach to the above "conventional" DSA, currently under way, is described in further detail. The methodology relies on a correlation model relating significant power system measurements with local loadability margins. Results of some tests on the Italian power system are presented and discussed.