Voltage stability assessment: Extended analysis on the italian power system

The paper presents the results of extended analysis aimed to evaluate the voltage collapse margin in the Italian electric power system, carried out through a dedicated application developed within a joint project between TERNA [the Italian transmission system operators (TSO)], centro elettrotecnico sperimentale italiano (CESI) and Milan Polytechnic. The application, based on a Quasi Steady-State (QSS) stability assessment method, is aimed at the preventive and realtime evaluation of the voltage collapse margins in the Italian power system through a set of indices which also allow to identify the critical areas and the most dangerous line trips. In particular, the procedure is divided into two different time horizon: the day ahead stage, aimed to perform a deep analysis on the data coming from the market, and the online stage aimed to check the assessment performed by the day ahead procedure, taking into account also the real-time tele-measurements and the state estimations available online by the electric power system supervisory control and data acquisition (SCADA). The paper mainly deals with the day ahead voltage stability evaluation and presents the results obtained on the basis of a set of test carried out on a detailed model of the Italian network.