Power Quality Indices in Liberalised Markets

Power Quality has recently become a pressing concern in electric power systems; the reasons are the increasing number of perturbing loads, the susceptibility of loads to Power Quality problems and, mainly, the new liberalized competitive markets, in which electrical disturbances have significant economic consequences and the customers have more importance due to the possibility of choosing the utility by which they are served. In practice, the new liberalized markets throughout the world are changing the framework in which Power Quality is addressed, and, today, Power Quality objectives have become of great importance for all power system operators. In particular, this book deals with Power Quality indices, which are a powerful tool for quickly quantifying Power Quality disturbances and serve as the basis both for illustrating their negative impact on power system components and for the compliance with the required Standards or Recommendations within a regulating framework. Both traditional indices, which are currently in use today, and new indices, which seem to be particularly useful in the future for solving Power Quality problems following deregulation, are taken into consideration. The book has six Chapters. Chapter 1 begins with some background concepts concerning the main classifications, causes and effects of Power Quality disturbances and some notes about the link between Electromagnetic Compatibility and Power Quality disturbances. Then, the traditional indices are introduced, i.e. the indices most frequently used in international standards, recommendations, or in the relevant literature. Chapter 2 illustrates new indices for assessing responsibility between utility and customers. The problems associated with the Power Quality disturbance source are analysed, including locating the PQ disturbance source, assigning responsibility for the disturbance, and identifying the “prevailing source” of disturbance, which is the side that contributes more to the Power Quality disturbance level. In Chapter 3, indices for non-stationary waveforms are analysed. This topic is particularly important because, for such waveforms, the needed information cannot be deduced easily from only the analyses of their spectral components, since their location in time must also be known. Also some advanced methods that are useful for overcoming difficulties that can arise in the analysis of power system waveforms, such as spectral leakage problems, are addressed; in particular, this Chapter deals with the theoretical background of these methods and their application to the calculation and proposal of Power Quality indices. Global indices are presented in Chapter 4. The goal of global indices is to quantify the quality of the whole supply voltage at a monitored site by means of only one figure or, at most, two figures. Global indices which are based on the comparison between ideal and actual voltages, based on the proper treatment of traditional indices, and based on the economic impact on the customers, are shown. Chapter 5 deals with the problem of the definition of an adequate assessment of Power Quality levels in an electrical distribution system in the presence of dispersed generation (DG); in particular, probabilistic indices are illustrated that take into account the variation in terms of Power Quality disturbance levels in the presence of DG. Finally, Chapter 6 addresses some of the economic aspects of Power Quality disturbances. First, the focus is mainly on the cost associated with PQ disturbances and on the indices that are more sensitive for making good cost estimates. Then, some economic mechanisms for PQ regulation, which are based on financial penalties, incentives or both, are discussed. Comprehensive coverage of the topics in the six chapters would have been much more extensive than the material presented in this book. However, in the interest of brevity, the authors have attempted to make the reader aware of the various issues as succinctly as possible.