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Bringing New Visualization Tools for the Detection and Mitigation of Dynamic Phenomena in the Transmission System

par Sezi, Tevfik T.S.;Warichet, Jacques ;Genet, Benjamin ;Maun, Jean Claude
Référence CIGRE Session(42: 24-29 August 2008: Paris), CIGRE Session 2008
Publication Publié, 2008-08

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Résumé :

Among the latest developments in technology, Wide-Area Measurement Systems (WAMS) are being implemented in many power systems around the world. The centralization and exchange of synchronized measurements allow gathering many accurate data, but rough data must be processed to generate valuable information to the system operator, that could complement the information alreadyavailable from the SCADA.For example, the geographical representation of voltage phase angles measured by Phasor Measurement Units (PMU) allows to easily identify flow transfer directions. Update at a high rate of this picture further allows monitoring the impact of various events, like the weakening of transmission corridors. However, these rough data representations have limitations when dealing with dynamic phenomena.This paper focuses on the critical information needed to detect dynamic phenomena in the power system, and on the way to efficiently present this information to the operator. This information can be qualitative, to help understanding the system behavior, but quantitative information will help the operator to assess the gravity of the situation. Therefore, comprehensive indices must be used, with adequately chosen threshold levels to initiate preventive or corrective actions. Graphical representation of these indices is also an important issue to facilitate the quick assessment of the system state by the operator. Specific tools have been developed for voltage stability and interarea oscillations, and examples are shown from simulations of realistic power systems.The assessment of the voltage stability of the power system uses indices computed on-line. The paper describes a new method using WAMS information and related to the electrical distance from each bus to the nearest generator. The combination of the time evolution and of a geographical representation of the indices allows giving a clear understanding of the status of the system.The crucial information to monitor interarea oscillations concerns the frequency, damping and mode shape of the oscillating modes. The mode shape indicates the involved areas and the way they swing with respect to each other, while the damping is used as index to assess the stability. A description is given of a PMU-based method developed to monitor those oscillations. Among the most interesting visualizations, the geographical view of the mode shape and the mode damping evolution with respect to time are selected. Both pictures complete each other and carry all the needed information, by showing on one hand the oscillating areas, and on the other hand the impact of small or major events on the system stability margins.