Power System Voltage Stability Carson W Taylor Pdf Free
Jahed Stetter
With contributions from worldwide leaders in the field, Power System Stability and Control, Third Edition (part of the five-volume set, The Electric Power Engineering Handbook) updates coverage of recent developments and rapid technological growth in essential aspects of power systems. Edited by L.L. Grigsby, a respected and accomplished authority in power engineering, and section editors Miroslav Begovic, Prabha Kundur, and Bruce Wollenberg, this reference presents substantially new and revised content.
This book provides a simplified overview of advances in international standards, practices, and technologies, such as small signal stability and power system oscillations, power system stability controls, and dynamic modeling of power systems. This resource will help readers achieve safe, economical, high-quality power delivery in a dynamic and demanding environment.
With five new and 10 fully revised chapters, the book supplies a high level of detail and, more importantly, a tutorial style of writing and use of photographs and graphics to help the reader understand the material.
Recent newsworthy wide-area electrical blackouts have raised many questions about the specifics of such events and the vulnerability of interconnected power systems when operated outside of their intended design limits.
Exchange of information stemming from worldwide blackout findings, restorative efforts, and innovations in technology shed new light on the current conditions, procedures, regulations, and design of power systems. Examination of the root causes, the resulting effects on neighboring systems, and implementation of proven solutions to help prevent propagation of such large-scale events should help us design reliable power delivery infrastructures for today and in the future. Armed with this detailed and fresh prospective, power industry professionals can consider the costly lessons of the past, maintain a library of historical lessons about "What and why it happened?" for generations to come, and act as catalysts to help design or revise power systems to a heightened reliability.
Although large-scale blackouts are very low probability events, they carry immense costs for customers and society in general as well as for power companies. It is easy to misjudge the risk of such extreme cases, and in particular the financial risk. Financial risk is the product of the associated cost and the probability of occurrence, and both factors are very hard to assess accurately. The need for extensive mitigation strategies against grid congestions and the high cost associated with such improvements, combined with inaccurate probabilistic assessments have led to risk management not focusing on appropriate, cost-effective mitigation actions. From a broader prospective, a misconception may be formed about the grid reliability or its exposure to large-scale outages.
Understanding the complexities of the interconnected power grid and the need for proper planning, good maintenance, and sound operating practices are key to preventing the problems of tomorrow for this modern-day necessity. This article offers practical explanations by experienced power industry navigators (from utilities and vendors, consultants, and academics, all with international reputations) on the leading causes of widespread blackouts and how best to prevent them in order to craft a steady course along the journey toward higher levels of reliability in future power generation and delivery.
Our lives continue to be improved by evolutions in technology, which include precision surgical equipment for use in critical operations; the revolution of information exchange through Internet and wireless technology that affects every aspect of our personal and professional lives; automatic banking anytime of the day; use of electric rail systems to reduce harmful emissions; and improved home appliances. Thanks to affordable costs and marketing concepts, many of the technological innovations achieved in the past quarter century have readily found their way into our daily lives.
The modern-day amenities and our respect for the environment have also increased our dependence on energy, hence our expectations for uninterrupted reliable power. Twenty-first-century equipment is entering our homes. Robotic appliances that perform all household duties are a reality within reach. Imagine: we arrive home and nothing is done due to unavailability of the electricity. That is if we manage to get home due to traffic jams caused by traffic lights not working or the rail system not running.
Modern technology is the catalyst driving power delivery, demanding grid reliability, and the marked increased dependence on availability has raised the bar on human expectation. However, the demand for the availability of power for much of the modern-day equipment has not been systematically and uniformly considered.
Let us consider our willingness to pay the price for availability. We are willing to pay more for a laptop computer with rechargeable backup battery than for a desktop computer so that we have a computer available when traveling. One can add the costs and environmental impact for discharging the batteries to further emphasize the price we are willing to pay for availability. Another example are hybrid automobiles where the price for clean-air vehicles continues to drop; yet we are not eager to use them as mileage between fueling (availability) is not as good as with regular cars or it takes much longer to charge up as opposed to gasoline fueling. The above analogy can be applied to power systems as well. There is a price for availability, and one can apply a fraction of the price difference to everyday conveniences we have become accustomed to in order to realize the hefty price we would be paying when availability becomes top priority.
The North American and the European grid systems that experienced blackouts in 2003 are among the most reliable systems worldwide. However, the same systems are subject to a host of challenges: aging infrastructure, need for generation sitings near the load centers, transmission expansion to meet growing demand, and regulatory pressures.
One of the challenges facing the power industry today is the balance between reliability, economics, the environment, and other public-purpose objectives to optimize transmission and distribution resources to meet the demand. These issues must be addressed to move the electrical system into the 21st century.
Resources and transmission adequacy are necessary components of a reliable and economic supply. Although reliability and market economics are sometimes driven by conflicting policies and incentives, they cannot be separated when the objective is reliability and availability. Today, grid planning faces an extremely difficult task given the challenge to achieve resource adequacy in our restructured industry, as market economics and local concerns often drive the decision for generation facility siting far away from major load centers.
Equally difficult is planning for an adequate transmission system when the location of future generation facilities is uncertain and the lead time for transmission construction is several times greater than that of the generation siting process and implementation.
It is more important than ever to find ways to project transmission and distribution growth, identify cost-effective solutions to deploy, and to determine criteria to be applied to guide prudent investment decisions. Some of the key areas to address are:
The need for regulatory bodies to step up and address matters such as defining and enforcing the standards for reliability, streamlining the right-of-way access for transmission, vegetation management vs. environmental impact, and the recovery on stranded investments to name a few items.
The price for reliability, the costs and risks that transmission owners and customers are willing to assume. The power industry is accustomed to optimizing investments and evaluating return on investments based primarily on financial aspects of trading energy and serving load within certain reliability criteria. This is done without considering financial aspects of unavailable energy (from undue service interruptions) due to low reliability and slow restoration that incurs significant costs to society, as recent blackouts have shown. This is an incomplete financial model that results in sub-optimal investment strategies.
Electricity is the key resource for our society; however, it has not been a priority for strategic planning. Cities, households, and industries will all suffer if the approach does not change and the identified major action plans are not implemented.
The grid is a tremendously complex system, and the interconnections that allow us to benefit from higher reliability and lower costs have also caused the domino failures experienced in many parts of the world in recent years. Although there is a tendency to point at one or two significant events as the main reasons for triggering cascading outages, major blackouts are typically caused by a sequence of multiple, low-probability contingencies with complex interactions.
Low-probability sequential outages are not anticipated by system operators or may develop too fast for human interactions, thus rendering the power system more susceptible to wide-area blackouts. As the chain of events at various locations in the interconnected grid unfolds, operators may not be able to act quickly enough to mitigate fast-developing disturbances. Operators are exposed to a flood of alarms and, at times, incomplete information. There are many factors to consider when human actions are expected, such as:
Concerns surrounding taking unpopular actions such as disconnecting customers (may later be subject to a line of questioning or proposed training if these actions were inadequate or exceeded the required response).
Power systems are designed to allow for reliable power delivery in the absence of one or more major pieces of equipment such as lines, transformers, or bulk generation, commonly referred to as contingency conditions. For example, North American Electric Reliability Council (NERC) Planning Standard IA sets forth the performance requirements a system must meet for various contingencies. The complexity of the grid operation, however, makes it difficult to study the permutation of contingency conditions that would lead to perfect reliability at reasonable cost. An accurate sequence of events is difficult to predict because there is practically an infinite number of operating contingencies. Furthermore, with system changes--e.g., independent power producers selling power to remote regions, load growth, new equipment installations that cause significant changes in power flow--these contingencies may differ significantly from the expectations of the original system designers. There have also been cases of system disturbances caused by scheduled equipment outages when the electrical system has not been adjusted, for continued safe operation, prior to the equipment being removed--again pointing to the complexity of the power grid.
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