An implementation of two-stage hybrid state estimation with limited number of PMU

State estimation is an important tool for power system supervision and control and the related applications. Based on the redundant measurements taken in the network, state estimation provides the most likely state of the power system. Conventional measurements were collected by the SCADA system and the measurement chain did not allow measurement synchronization. A disadvantage is that due to the communications delay measurements inherit an additional error and simultaneously voltage angle measurements are not available. With the advent of phasor measurement units (PMU's), synchronized phasor measurements are possible. It allows to enhance the performance of state estimators. Expecting the gradual penetration of PMUs this paper discusses possible hybrid SE methods, integrating partial PMU measurements into the classical SE systems.