Monitoring of frequency disturbances in the European continental power system

Generation from non-programmable renewable energy sources, which is endowed with dispatching priority but is not always required to participate in ancillary services, has massively increased its share of demand supply in recent years; thus, a reduced number of large conventional power plants is left to be dispatched. Therefore, active power imbalances in AC power systems can lead to more severe frequency transients (minimum/maximum instantaneous and quasi-steady-state deviations), since less operational reserves are available to contain frequency deviations and less rotating machine inertia is online to reduce the absolute value of the Rate Of Change Of Frequency (ROCOF); thus, frequency stability can be jeopardized. This paper describes some results of an experimental activity focused on the measurement of system frequency and of the ROCOF. The main features of the measurement algorithms are presented. Statistical analyses of the data collected at a low-voltage node in the European continental interconnected system over a one-year time interval are reported. A preliminary analysis of large power plant outages impacting on frequency behavior is shown.