The secondary voltage regulation in Italy

Improvements in the automation of transmission network voltage control has become a challenging problem. In this framework, the paper preliminarily describes the basic concepts of the secondary voltage regulation (SVR) and the hierarchical control system under application to the overall Italian transmission network for the voltage and reactive power regulation. At the power plant level this hierarchical control system operates through an innovative, microprocessor based, voltage and reactive power regulator, named REPORT. At the regional load dispatcher level, a regional voltage regulator (RVR) controls in real time and closed-loops through the REPORTs, the voltages of the main EHV buses in the region. Both the REPORT and RVR control apparatus have been designed and developed by CESI. The Italian Independent System Operator (ISO) has under way the general application of the REPORT apparatus to all the main power plants, a large amount of them being already in operation, as well as of the RVR regulators at the regional dispatchers control rooms. The paper describes the main characteristics and performances of the mentioned control apparatus, the progress of their application in the field, their impact with the traditional operation, and comparison with alternative voltage control service; significant field test results are also shown. Some considerations about the influence on the voltage service of the power system restructuring process are also given.