Current measurements to obtain state estimation

In this paper, the synchronized time pulses from Phase Measurement Units (PMU´s) or dedicated computer communications are used to resolve line current measurements into components that are in phase and out of phase with the slack (reference) bus voltage. The current components in turn are used to compute the State Estimate (SE) of the power system, i.e. the voltage magnitude and ac phase angle of every bus with respect to the slack reference. Current measurements are obtained from `bird-on-wire´ devices or else current isolation transformers, both of which are assumed to contain signal processing software computers. Because the current measurements are on a transmission or distribution circuit phase line, the state computed is the line to neutral voltage at an angle with respect to the slack reference. Distribution single and two-phase lines are considered, but aggregating three-phase current measurements provides the positive sequence equivalent. The methods of the paper are extendable to unbalanced three-phase systems.