Michele de Nigris*, Ferruccio Villa** Eurelectric – Ceer joint Workshop on Voltage Quality Monitoring Brussels, 18 Novembre 2009 PRESENTAZIONE POWER POINT * ERSE SpA ** AEEG The Italian power quality monitoring system QuEEN has been performing Power Quality (PQ) measurements in the MV distribution network since 2006 and on about 600 instruments distributed all over the Italian territory (400 units installed in HV/MV substations, 200 units installed along the MV lines ). The assessment of PQ performances across the country, during a long-term period campaign, could be very useful for regulation activity provided that the system is periodically submitted to some indispensable technical updating from the point of view of both measurement techniques and data evaluation methods. The presentation outlines the main results obtained during the first 3 years of operation of the system and the main learning of the monitoring campaign. In particular we present the lessons learned on the measuring system, with particular reference to the avoidance of “false positives”, on the system management, and on the data analysis. It is outlines that: • HV/MV station observation point is suitable to monitor what happens downstream (for dips) • Monitoring campaign shall cover several years as there is a wide variability of data on the single site in consecutive years • The single measurement point dip-performance shows high variability year after year • Nationwide, the dip-performance shows stable trends (variations 2-3% over the years) • About 30% of the events are transferred from HV networks • Multiple linear regression models are necessary to analyze the data and derive learning: in this respect, the factors having high influence proved to be the following: geographical aspects, length of overhead lines and neutral operation (isolated vs. compensated); factors having little influence were the length of underground cables and the system voltage. Lightning data correlation needs further analysis