Tolerancia al efecto de impedancia de falla en relevadores de distancia

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Coordinated static and dynamic reactive power planning against power system voltage stability related problems

Power System, over the many years, has undergone dramatic revolution both in technological as well as structural aspects. With the ongoing growth of the electric utility industry, including deregulation in many countries; numerous changes are continuously being introduced to a once predictable system. In an attempt to maximally use the transmission system capacities for economic transfers, transmission systems are being pushed closer to their stability and thermal limits, with voltage instability becoming a major limiting factor. Insufficient reactive power support affects the reliable operation of electric power systems leading to voltage collapses as observed by the recent 2003 blackout. Among the many available solution options, installation of reactive power control devices such as MSCs, FACTS devices etc seem more viable. This is a typical long term planning problem that needs to consider both steady state as well dynamic condition of the power system after severe contingencies and use better informative indices for the planning process.;A mixed integer programming based algorithm is made use of in this work to develop a comprehensive tool to perform a coordinated planning of static and dynamic reactive power control devices while satisfying the performance requirements of voltage stability margin and transient voltage dip. The systematic planning procedure is illustrated on a large scale case study. The effectiveness of the planning algorithm is demonstrated using two separate planning problems, one where steady state planning is done exclusively against static voltage stability problems, and the other where a coordinated steady state and dynamic Var planning problem is solved.;The results of this work show the effectiveness of the developed planning tool to find a low cost optimal reactive power allocation solution to enable higher real power transfers and improve voltage stability. We envision the method developed will be a research grade tool for planning reactive control devices against voltage instability and will provide system planners a proper guide to find viable and economical planning solutions

Operating strategies to preserve the adequacy of power systems circuit breakers

The objective of the proposed research is to quantify the limits of overstressed and aging circuit breakers in terms of probability of failure and to provide guidelines to determine network reconfigurations, generator commitment, and economic dispatch strategies that account for these limits. The proposed temporary power system operating strategies address circuit breaker adequacy issues and allow overstressed breakers to be operated longer and more reliably until they are replaced with adequate equipment. The expansion of electric networks with new power sources (nuclear plants, distributed generation) results in increased short-circuit or fault currents levels. As fault currents increase, they will eventually exceed circuit breaker ratings. Circuit breakers exposed to fault currents in excess of their ratings are said to be overstressed, underrated, or inadequate. Insufficient ratings expose overstressed breakers to increased failure probabilities. Extensive common-mode outages caused by circuit breaker failures reduce the reliability of power systems. To durably avoid outages and system unreliability, overstressed breakers must eventually be replaced. Large-scale replacements of overstressed breakers cannot be completed in a short time because of budgetary limits, capital improvement schedules, and manufacturer-imposed constraints. Meanwhile, to preserve the ability of old and overstressed breakers to safely interrupt faults, short-circuit currents must be kept within the limits imposed by the ratings and the age of these breakers by using the substation reconfiguration and generator commitment strategies described in this study. The immediate benefit of the above-mentioned operating strategies is a reduction of the failure probability of overstressed breakers obtained by avoiding the interruption of currents in excess of breaker ratings. Other benefits include (i) increased network reliability, (ii) restored operating margins with respect to existing equipment, and (iii) prioritized equipment upgrades that enhance the long-term planning of power systems.Ph.D.Committee Chair: Meliopoulos, A. P. Sakis; Committee Member: Divan, Deepakraj M.; Committee Member: Harley, Ronald G.; Committee Member: Johnson, Ellis L.; Committee Member: Taylor, David G