The implementation of a Web system information management for assessment of power quality indices and detection of critical zones on a distribution system is proposed in this paper. The proposed system was implemented on a APACHE server platform, consisting of three main parts. The first part registers, pre-processes and stores power quality measurements on an open source data base using MySQL. In the second part power quality indices are calculated for each substation, such indices allow the evaluation of disturbances like voltage sags, voltage swells, voltage flicker (Pst) and voltage unbalance. Finally, in the third part the indices are displayed as power quality maps by means (Google Maps) tools, where critical zones are identified for each disturbance according to disturbance activity and severity criteria. This is a low cost, useful and easy to implement tool by the network operator, also can be implemented by the regulatory body for end user consultations.