PMU Measurement Uncertainty Considerations in WLS State Estimation

A method to assign weights to the measurements obtained through phasor measurement units (PMUs) in a weighted least squares (WLS) state estimation is presented in this paper. The uncertainties for direct measurements are obtained from the manufacturer´s specifications. For pseudo-measurements, the uncertainties are evaluated by using the classical uncertainty propagation theory. The propagation of measurement uncertainty as a function of line length and conductor type is also investigated. The lower and upper bounds of the estimated states considering the measurement uncertainties are found by using linear programming. The proposed method is applied on the IEEE 14-, 30-, 57-, and 118-bus test systems, and the state estimation results including the lower and upper bounds of the estimated states are presented.