The QuEEN demonstration project for the monitoring of the voltage quality has been collecting a great amount of Power Quality data since February 2006, at 600 monitoring sites spread all over the Italian territory. In the first part of the presentation the system is described with its most recent updating, in accordance with the revision of the standard EN 50160. In particular all the improvements which have regarded some PQ parameters (voltage variations, voltage dips and swells) and the reporting methods of their statistics, are dealt here together with the characteristics of a new more effective filter for the “false” voltage dips identification which has become active in the system beginning from 2009. Thank to the vast amount of data acquired up till now by the monitoring campaign it has been possible to perform some kind of “out of line” data analysis relating to voltage dips statistic by both multilinear regression analysis and investigation of the historical trend of some indices, whose main results are briefly summarized. The second part of the presentation is focussed on some general considerations which can be drawn from the experience acquired by the demonstration system QuEEN. This part deals with the measuring methods, problems and possible solutions referring to the voltage dips measurement to follow with the management complexity required by a wide area monitoring system due to the arising of both operative and costs problems to end with some final considerations on PQ data analysis results.