Utilization of Phasor Measurement Unit Measurements as Basis for Power System State Estimation Interface

Utilization of phasor measurements units (PMUs) in wide area monitoring and control systems (WAMS), has a large potential for increased situational awareness in power system operation, especially regarding system stability surveillance. Applications utilizing PMU measurements, however, are still in their early stage. A measurement interface (MI) based on PMU measurements was developed as part of this thesis, as an example of a possible network information system (NIS) for control room purposes. Its main objective was to display the measured voltage and current phasors, as well as other significant power system parameters that could be derived, so that the current state of the system was accurately visualized, and its voltage stability could be assessed. The laboratory power system set-up consisted of a single generator, supplying a single load, and was subjected to increasing load power demand, and varying system impedance.A simulation model of the laboratory power system, was developed to validate the MI calculations. The theoretical basis of the voltage-power characteristic estimation, and VSI\down{SCC} voltage stability indicator, were proved incorrect for the power system set-up utilized in the experiments. The indicators might perform better in a high-voltage grid, with low resistance, and less dynamic load power factors, but this should be investigated further.During the laboratory experiments, it was discovered that only measuring a single phase in each measurement location, introduces deviations in the calculations, when applied to power systems that are not perfectly symmetrical. When implemented in an actual power grid, the PMUs should measure all three phases at each node, to increase the accuracy of the MI.The phasor diagram behaved correctly when based on both simulated and measured phasors, and provided a highly intuitive and accurate visualization of the current state of the system. This may significantly increase the situational awareness for the grid operator, and it might even prove useful for educational purposes, because of its natural ability to visualize the current state of the system.The trend curves visualizing phasor magnitudes, phasor angles, system frequencies, calculated powers, and impedances, will be great assets in every network information system, and provide valuable information to the grid operator. They are important parameters, since pattern recognition of these can 1) predict impending faults, 2) govern the supply-demand scheduling, 3) analyse primary frequency, or 4) validate power system models off-line. All of the parameters and displays developed in this thesis, except the voltage stability indicators and the voltage-power characteristic estimation, have been validated for power system operation, both during increasing load power demand, and varying system impedance. Even though the ISI voltage stability indicator was not tested close to its limit during real-time operation, it performed well on the simulated voltage and current phasors, and should therefore be included among the successful parameters. The developed network information system based on PMU measurements are sufficiently accurate, greatly improves the situational awareness delivered by the SCADA systems today, and provides invaluable information for the grid operators, regarding the real-time power system operation. The MI can be considered as proof of the WAMS concept, and should be investigated and developed even further in the future