In this thesis we describe an application for collecting and analyzing power quality data of electric distribution systems. The thesis is divided into three parts. We begin with a theoretical description of electric distribution networks and define power quality. We then describe the basics of quality monitoring systems and measuring devices, which are used to measure power quality in electric distribution network. The main contribution of this thesis is an implementation of MiSmart, a web platform for monitoring and analysis of power quality data. We describe the part of application named „Data monitor", which we developed in this thesis. MiSmart platform allows faster response to problems, efficient maintenance and provides better power quality in electrical distribution networks.