In modern EMS, state estimation is used as a tool for monitoring how the power system operates. A state estimator iteratively calculates the voltage profile of the currently operating power system with voltage, current, and power measurements gathered from the entire system. It is usually assumed that all the measurements are obtained simultaneously. It, however, is not practically possible to maintain the synchronism of the measurements data. Recently, phasor measurements synchronized by satellites are used for the operation of the power systems. This paper describes the state estimator modified to support the processing of synchronized phasor measurements. Synchronized phasor measurements are found to provide synchronism of measurement data and improve the nccuracy/redundancy of the results of running it are presented.