Excessive integration of distributed generation units, electrical vehicles and batteries makes the online monitoring of the distribution system vital in terms of operation and control of the power systems. In transmission level, most of the countries have their online monitoring systems which are SCADA, Energy Management Systems or Wide Area Monitoring Systems. However, this case is not valid for distribution systems since there are thousands of nodes and branches that need to be monitored. In this paper, optimum allocation of micro-synchrophasors is performed on a real radial distribution system feeder which is situated in the northwest region of Turkey. Based on optimally allocated micro-synchrophasors, distribution system state estimation has been carried out and the results have been validated by simulating the given power distribution system in PSS Sincal simulation program.