Showing papers in "IEEE Computer Applications in Power in 2002"

PCB Rogowski coils benefit relay protection

Abstract: Innovative Rogowski coils enable the design of advanced protection systems when used with new multifunction relays and fiberoptic communication. The protection systems have faster response times to faults and can easily adjust to load and/or power system configuration changes. Since the new Rogowski coils are very accurate and do not saturate, protection levels can be set to lower fault current thresholds, reducing the stress on the protected equipment. The whole system is immune to external magnetic fields and has self-testing logic. No wiring is necessary.

Future trends in power system control

Abstract: To buy time for online computations needed for central coordination and to attain wider-area objectives for optimum operation, one has had to resort to decomposition and, therefore, multilevel hierarchical control schemes. This article looks into the future state of power system operations and control based on a number of assumptions and provides an analysis of the direction that this area might take over the next 25 years. Issues related to development of techniques and requirements for fully coordinated, high-bandwidth, and robust controls for power systems are discussed, and some methodologies are suggested. Proceeding toward this ultimate goal, system-wide automatic voltage control (SAVC), system-wide automatic power control (SAPC), and the integrated system-wide automatic control (SAC) concepts are introduced for coordination of injection (shunt) and routing (series) controllers for both real and reactive power.

Internet-based SCADA display system

Abstract: In the deregulated environment, information is the key to secure operation, profitability, customer retention, market advantage, and growth for the power industry. The rapid development of the Internet and distributed computing have opened the door for feasible and cost-effective solutions. This article describes and demonstrates a unique Internet-based application in a substation automation system that is implemented based on the existing system control and data acquisition (SCADA) system and very large-scale integration (VLSI) information technologies (IT). The user can view the real-time data superimposed on one-line diagrams generated automatically using VLSI placement and routing techniques. In addition, the user can also control the operation of the substation at the server site. The choice of Java technologies, such as Java Native Interface (JNI), Java Remote Method Invocation (RMI), and Enterprise Java Bean (EJB), offers unique and powerful features, such as zero client installation, on-demand access, platform independence, and transaction management for the design of the online SCADA display system.

ANN approach assesses system security

Abstract: Large interconnected power systems with dispersed and geographically isolated generators and load constitute a majority of the power network. Present-day power systems are dynamic in nature, where the network topology frequently changes with load demand. With increase in load, the power system network is loaded to its limits, making it susceptible to collapse even under minor disturbances. In order to operate the power system economically, the current operating state of the system must be identified as either secure or insecure. An artificial neural network (ANN) aided method for security assessment is proposed and illustrated for a model six-bus power system. The work demonstrates the feasibility of classification of load patterns for power system static security assessment using a Kohonen self-organizing feature map. The most important aspect of this network is its generalization property. Using 15 different line-loading patterns for training, the network successfully classifies the unknown loading patterns. This powerful and versatile feature is especially useful for power system operation. Research is in progress to include contingency analysis in the security assessment program.

Shipboard power restored for active duty

Abstract: Network reconfiguration for restoration in a military shipboard power system is a very important task that is performed in order to restore loads as a result of battle damage or system faults. This article features an expert-system-based reconfiguration methodology for load restoration in shipboard power systems. The power system considered in the present study is based on the layout profile of a US surface combatant ship. The methodology developed will determine whether the loads that lost supply are restorable. When considering loads, it gives precedence to high priority loads. It also determines if there is any violation of current constraints of any cables and voltage constraints at load nodes. If the load is restorable, as suggested by an expert system, and there is no violation of any constraints, then the load is said to be restorable and the operation sequence required in restoring that load would be given as the output. A CAD drawing of the power system and a database of the system information has been developed using a geographic information system (GIS). A software tool incorporating failure assessment and expert system restoration methodology was developed using Visual C++, Multilogic Exsys Developer, Alternate Transients Program (ATP), and Microsoft Access. Microstation has been used for GIS. Various fault cases were designed, and the developed tool was used to run them and perform expert system restoration.

Integrated ANN approach to forecast load

Abstract: The demand for electricity is known to vary by the time of the day, week, month, temperature, and usage habits of the consumers. Though usage habit is not directly observable, it may be implied in the patterns of usage that have occurred in the past. A short-term load-forecasting (STLF) program that uses an integrated artificial neural network (ANN) approach is capable of predicting load for basic generation scheduling functions, assessing power system security, and providing timely dispatcher information. How well training data is chosen in an ANN is the defining factor in how well the network's output will match the event being modeled.

Web-based simulations of power systems

Abstract: This article describes an attempt to create a completely Web-based, platform-independent, power system simulation package with various analyses distributed in a clustered environment. This is done in order to retain many of the existing simulation routines that have already been implemented on multiple platforms while sharing many common facilities and resources. It achieves this by leveraging heavily on the advanced distributed computing technologies and by using the model-view-controller (MVC) concept. Applying this design concept demonstrates the potential and advantages of embracing the Web as the platform for developing and deploying complex power system simulations.

Control centers are here to stay

Abstract: are thorns in the side of the free marketer, who might grumble in exasperation: “Why don’t engineers just pack up and go home?” But, engineers and control centers are here to stay. An integration of hardware components, software functions, graphical user interfaces, communications, and (not least), the human operator, the control center is the quintessential computer application in power. Articles have appeared in CAP magazine throughout its publication history on various control center installations, software applications, communication networks, and standards. This article focuses on the energy management system (EMS) control center, identifying the major functions that have become standard components of every application software package. The two most important control center functions, security control and load-following control, guarantee the continuity of electric ser-

Information Highway

Abstract: Fully committed to making maximum use of the speed and efficiency of the Internet, the IEEE Power Engineering Society (PES) has made dramatic progress along the information superhighway in the past year. That’s not to say we didn’t encounter the occasional detour and speed bump along the way, but our advancement in electronic services to our members can now be measured in kilometers rather than centimeters.

Deriving model parameters from field test measurements

Abstract: ISSN 0895-0156/02/$17.00©2002 IEEE Amajor component of any power system simulation model is the generating plant, which comprises three major subcomponents of interest: the generator, excitation system, and the turbine/governor. Accuracy of representation is dependent both on the structure of the component models and the parameter values used within those models. Since the accuracy of power system stability analysis depends on the accuracy of the models used to represent the generators, excitation control systems, and speed governing systems, the parameters used in those models could affect the calculated margin of system stability. Use of more accurate models could result in increases in overall power transfer capability and associated economic benefits. Alternately, inaccurate simulation models could result in the system being allowed to operate beyond safe margins. To assist in these efforts, Power Technologies, Inc. (PTI), the New York Power Authority (NYPA), and EPRIJ.W. Feltes and S. Orero are with Power Technologies, Inc., Schenectady, New York, USA. B. Fardanesh, E. Uzunovic, and S. Zelingher are with the New York Power Authority, New York, USA. N. Abi-Samra is with EPRIsolutions, Inc., Palo Alto, California, USA. Deriving Model Parameters from Field Test Measurements

Verifying resonant grounding in distribution systems

Abstract: ISSN 0895-0156/02/$17.00©2002 IEEE F ollowing deregulation within the electricity sector, the quality of electric power supply is a key factor for distribution companies. There has been a considerable increase in the number of users with equipment that is vulnerable to minor interruptions. One way of improving power quality is to use resonant grounding whereby the compensatory effect of the coil minimizes the fault current and allows service to be maintained during a fault. The disadvantage posed here is the difficulty of selective fault detection, which is, in fact, due to the low levels of fault currents. I. Zamora, A.J. Mazón, K.J. Sagastabeitia, O. Picó, and J.R. Saenz are with the University of the Basque Country, Spain. Verifying Resonant Grounding in Distribution Systems

Power electronics spark new simulation challenges

Abstract: ISSN 0895-0156/02/$17.00©2002 IEEE T he computer simulation of power systems has presented many challenges and opportunities over the years. Fortunately, the general nature of power systems remained relatively the same for a long period of time. This allowed power system engineers to improve modeling techniques progressively and to apply computer hardware and software technology to design study tools that met the analysis requirements. The models were based on fundamental frequency responses. However, with the wide-spread use of microprocessor-based controls and the associated advances in power electronic devices over the past 10 years, the nature of modern power systems has significantly changed. This article discusses some of the changes that have taken place in power systems and explores some of the inherent requirements for simulation technologies in order to keep up with this rapidly changing environment. Industrial examples of how power system simulation has been applied by end-users to meet the advancing requirements is provided.

Auto-check circuit breaker interrupting capabilities

Abstract: Circuit breakers in a utility network are designed to quickly isolate short-circuited equipment from the rest of the system. The short-circuit current changes with switching operations and with the addition and removal of generating sources. Hence, electric utilities must check their breakers periodically using computer simulation to ensure that the breakers are capable of interrupting the short-circuit currents. The recent proliferation of independent power producers (IPP) has made breaker-rating studies a much more routine procedure for utility engineers. The aim of these studies is to see if the existing circuit breakers are adequate when the proposed generators are put in service. The need for efficient and accurate breaker-rating software is greater now than ever. The benefit of computerized breaker-rating studies has been recognized for many years. Most utilities have breaker-rating software of some kind. What is not well known about breaker rating is the inherent difficulty in rating breakers using the sequence-network model that is commonly used for short-circuit studies. The breaker-rating program was improved by making the description of the breaker more flexible, universal, and easy to apply. This is the breaker connection model.Once breaker data is entered into a database, a breaker-rating program greatly reduces the time and effort required to ensure that breakers will work property in the event of a fault.

Managing risk in the new power business: a sequel

Abstract: As the power business is moving into new territory with market deregulation, there is a need for expressing a view on financial and physical risks. By means of an example published earlier in this magazine, we discuss what could be appropriate measures of risk for a producer. In the article by M.V.F. Pereira, et al. "Managing Risk in the New Power Business," (see ibid., p.18-24, April 2000), management in the deregulated power markets is discussed. The article is valuable, both in its reflection on risk and its description of market issues. However, a central theme that resonates throughout the article involves the use of min-max regret as a method for controlling risk in the decision-making process. We have observed that the use of this measure is, itself, a "risky" prospect, largely because its conclusions can be so sensitive to the manner in which the problem is posed. In response to this observation, we suggest alternative approaches to risk management.

Simulation model explores alternative wholesale power market structures

Abstract: The power crisis in California from the summer of 2000 to the spring of 2001 caused great interest and concern in the power industry about deregulation and liberalization of the wholesale power market. In response to this interest, EPRI has developed a prototype computer simulation model to study alternative wholesale power market structures. The results were presented at a workshop organized jointly by the California Energy Commission and EPRI on 7 November 2001 in Sacramento, California. This article is based on that presentation and represents work in progress. There are four objectives of developing and applying the EPRI Long Term Power Market Simulation Model (LTPMS): improve the understanding of how a competitive power market works in the long term; study the potential price volatility and boom-bust cycles of the power market; study alternative market designs and the role of a power authority to complement the market; and compare the long-term impacts of various market structures on the end-users and society.

Restructured Electric Power Systems: Operation, Trading, and Volatility [Book Review]

Abstract: The electric power industry is in the midst of a major restructuring in which electric energy would be traded as a commodity, electric power markets would foster open access to all suppliers of electric power, discrimination against any user of the transmission system would be reduced or eliminated, a competitive wholesale market at the national level would be fostered to reduce prices, and a competitive retail market at the state level would be encouraged to provide customer choice and competition in service and reliability. Ultimately, small customers will be able to choose their electric supplier much as they currently select their long-distance telephone carrier. For decades the electric utilities monopolized the way power was generated, transmitted, and distributed to customers in their service territories. Utilities were vertically integrated and provided generation, transmitted power in bulk from generating stations to load centers, and distributed power to customers. Although these three components remained the same, where restructuring brought on by deregulation has occurred, the three services were unbundled. Furthermore, coordination and rules were established to guarantee competition and nondiscriminatory open access to all users in the interconnection. These changes were brought about by a series of FERC Orders that progressively changed the environment in response to how the industry responded and how FERC felt it measured up to its objectives for a competitive, efficient marketplace. The energy shortages and rolling blackouts in California and elsewhere suggest that the evolution from a monopolistic to a competitive marketplace has not always been smooth. Restructured Electric Power Systems: Operation, Trading, and Volatility provides the reader with information without taking any position for or against any of these FERC Orders. It provides rational pro and con arguments made as these FERC Orders were discussed prior to implementation and the reasons that FERC gave for issuing the orders in their final form. The authors provide unbiased reporting of background information. Fortunately for the reader, they selected a self-consistent set of topics that could be covered in a book about operation under a restructured electric power system environment. The book covers the following developments: A competitive marketplace needed new trading-based methods for scheduling which generators and services would be provided for whom and by whom. This was carried out in detail for various restructured systems. A second level of concern existed, regarding what level of generation and what level of service each of the scheduled generators and control devices would provide based on the marketplace trading. This was also carried out for several restructured systems. The transactions and limitations of the trading marketplace-based operation process must be transparent in order to bolster customer and supplier confidence. Thus, the Open Access Same-Time Information System (OASIS), a reporting process and system, was implemented. A discussion of OASIS, the information it provides, and how it is determined is given Energy shortages or congestion in the interconnection that restrict the flow of power are two of the many previously unknown risks that can cause market volatility in a monopolistic environment. Market-based vehicles were needed and created to reduce and manage each of the risks identified. The risks and the various vehicles created to manage each risk are discussed. A comparison of the marketbased operating structures for various regions of the United States is provided, and a comparison of restructuring in several foreign countries is given in

Unmanned substations employ multimedia network RTUs

Abstract: The so-called "multimedia network RTU" featured in this article integrates real-time video capturing and transmission, audio analysis and electric equipment diagnosis, global positioning system (GPS), substation security supervision, and Internet protocol (IP) communication into traditional RTUs. This article: Describes three key features of the proposed system distinguishing it from the existing RTUs Details the hardware and software architecture and functions of MNRTU Provides a typical application example in Shanxi province that verifies the availability and advance of MNRTU.

Right power, right price [enterprise energy management systems]

Abstract: Beyond price, large energy consumers are increasingly demanding higher value for their energy investment. For many businesses, especially those that are part of the burgeoning digital economy, this includes an expectation of energy delivered at higher levels of quality and reliability. These factors are driving enterprises on both the supply and demand side of energy to seek better strategies to manage the cost and quality of the energy product and the energy assets that produce, deliver, control, and consume it. However, to achieve this, all enterprises face three very large and fundamental challenges, which are the needs to: support the economic and efficient delivery, purchasing, and use of energy, guarantee higher levels of power quality and reliability the grid cannot currently deliver Supply the increasing demand for energy while establishing a market-based pricing system. The key to addressing all of these challenges is an Internet-enabled enterprise energy management (EEM) system that delivers real-time information and control through an efficient, economical, and scalable architecture.

AI automates substation control

Abstract: The control of a substation is a very complex task due to the great number of related problems and, therefore, the decision variables that can influence the substation performance. Under such circumstances, the use of learning control systems can be very useful. The difficulties associated with the application of artificial intelligence techniques include: selection of the magnitudes to be controlled; definition and implementation of the soft techniques; and elaboration of a programming tool to execute the control. The interest of the present work is to expose the obtained results and to present them for discussion. The objective is to show that it is possible to control the status of circuit breakers (CB) in a substation making use of a knowledge base that relates some of the operation magnitudes, mixing status variables with time variables and fuzzy sets. Even when all the magnitudes to be controlled cannot be included in the analysis (mostly due to the great number of measurements and status variables of the substation and, therefore, to the rules that would be required by the controller), it is possible to control the desired status while supervising some important magnitudes as the voltage, power factor, and harmonic distortion, as well as the present status.

Prospective on computer applications in power

Abstract: he so-called \" deregulation \" and restructuring of the industry have made it very difficult to keep up with industry changes and have made it much more difficult to envision the future. In this article, current key issues and major developments of the past few years are reviewed to provide perspective, and prospects for future computer applications in power are suggested. Technology changes are occurring at an exponential rate. The interconnected bulk electric systems are becoming integrated with vast networked information systems. This article discusses the skills that will be needed by future power engineers to keep pace with these developments and trends. The computer applications used in the electric power industry have undergone profound changes since the first issue of IEEE Computer Applications in Power in January 1988. During that period of time, those of us who have had the privilege of working for electric utilities, electric utility organizations, and organizations providing services and products for the electric power industry have seen: I Development of new techniques for improving the increasingly vast quantities of real-time data being acquired I Availability of lower cost faster computers as well as great reductions in the cost of memory I Enormous increases in engineering productivity and increasing requirements for engineers to function in more complex roles I Shift in energy technology preferences concomitant with concerns about resource reserves, public safety, and environmental protection I Globalization of equipment markets and the recognition of the need for international standards I Advent and widespread acceptance of computer networking applications using the Web I Development of methods to accommodate real-time competitive power markets associated with industry deregulation/ restructuring. I Development of flexible ac transmission system (FACTS) technologies and new procedural methods for coping with transmission system congestion I Upgrades to relaying systems,

Automated network control and supervision

Abstract: At energy markets driven by deregulation and liberalization processes under way in central and eastern European countries, information and its processing is gaining key importance. Energy trading will require risk management of multiple aspects of power engineering, and decision-making and implementation-support tools will be increasingly helpful. The need for computer support is of particular concern to network companies. Just like control and supervision systems, computer support is subject to far-reaching technical and functional integration. The dynamic development and dissemination of microcomputing technology as well as the transition to a market-oriented approach of power engineering makes this possible, and the introduction of automatic control and supervision systems at all voltage levels is required. This includes distribution lines and substations. The cost of such solutions is decreasing at the present time and may be treated as justified costs in networking power utilities due to increased requirements for energy supply and customer services. This article deals with some main issues of automatic control and supervision systems development and their integration into the general functions of networking power companies. It also discusses common technical frameworks, including their potential application at the national power engineering level.

Automating motor-operated air-breaker switches

Abstract: The detection and clearing of transformer faults are intimately connected to the primary switching that is available. Breakers are used both as locations for the current transformers to detect a fault and define the zone of protection and as a way of clearing the fault. The use of so many circuit breakers (CB) is usually not justified economically. As an alternative, motor-operated air-breaker switches (MOAB) instead of CBs are commonly used. A MOAB cannot interrupt a fault and usually can be opened only if the adjacent transmission line segment is de-energized. The growth and increased complexity of power system configurations has led to arrangements of MOABs with transformers and power transmission lines. This causes a difficult situation when relay engineers coordinate operation of relay sequence and MOABs. This article presents a solution for such a difficulty. The solution utilizes a local area supervisory protection (LASP) system to collect voltage and current data and then share data among the associated relays.

IT strategy in the Texas energy market

Abstract: The Texas Electric Choice Act, signed in 1999, cleared the way for the deregulation state's electricity market. The Electric Reliability Council of Texas (ERCOT) has slated 1 January 2002 for the opening of Texas' electric power market to full retail competition. The pilot market was opened on 31 July, with wholesale deregulation and retail access allowed for 5% of the total retail market. Presently, there are 30 firms certified as qualified scheduling entities (QSE) to participate in the restructured Texas market. Each of these companies faces a variety of IT requirements for communications, analysis, and operations in order to do business in ERCOT's territory. This article focuses on identifying these needs and discusses the IT solutions that must be deployed to meet them.

Power station GIS design and implementation

Abstract: In power station management information systems (MIS), an important function is to manage electric facilities (e.g., equipment of main workshop, pipelines). Electric facilities have obvious features: their number is large and they are geographically related. The number of pipelines can reach about 40 types. Most pipelines are under ground and constitute very complicated networks. During the construction and development of a power station, these networks are changed at different extents. It is clumsy to modify paper maps, and paper maps easily become obsolete and are easily damaged. In addition, when the power station needs new buildings or needs maintenance work to pipelines, the worker should know their geographical distribution. These problems can be solved efficiently using GIS. In the facility management of power stations, facility maintenance management is a very important part, including heavy repair, routine maintenance, and facility defect management. At present, there has been mature management software for equipment maintenance and repair. Integrating these with GIS can enhance visual and graphical effects. Because of the large amount of equipment and the complexity of the pipeline network, the management requirements for administrators are very high. Applying GIS and network technology to power stations can implement centralized and graphical management of pipelines, equipment, workshops, and geographical related information and can provide data sharing, modern management methods, and decision-making support.

Reliability simulation shows results

Abstract: While traditional engineering applications have been used to address power quality, voltage, and various other issues within the distribution system, the presentation of these results normally has been within an engineering audience. However, today's engineer often needs to perform reliability studies and present the results to a much wider audience, including utility executives, managers, customer support, utility commissions, and even energy customers. As a result, reliability studies can become extremely important and often influence business decisions. This article addresses the challenges of results presentation to this larger audience, as well as preparation of the data required for a comprehensive study that will satisfy audience expectations.

Prioritizing reliability for underground distribution

Abstract: US domestic power utilities are faced with over 600000 kilometers of solid-dielectric underground cables, virtually all of which do not meet the reliability standards required of a twenty-first century economy. Diagnostic testing methods are being developed and commercialized that are intended to prioritize the 600000-kilometer cable replacement effort. Over 90% of the pre1980 vintage cables are single-phase underground residential distribution (URD) cable. An economic model is presented that allows an objective comparison of any testing technique and the alternatives, which include replacing the suspect circuits or using commercially available life-extension technologies. Available diagnostic technology is not an economically viable option for URD cables. An alternative computer-based tool is now available that aids in the prioritization efforts at a small fraction of the cost of performing diagnostic testing. The tool provides a strategic reliability analysis (SRA), which allows the mining of the utility's own data to definitively answer the critical strategic questions.

Managing MV networks for quality of service

Abstract: In today's deregulated marketplace, simply delivering power to customers is no longer sufficient; utilities must provide a certain level of quality of service and must deliver the commodity safely, reliably, and cost-effectively. Moreover, information traditionally used only within a given utility is now desired by many players, since the integration, consolidation, and dissemination of information both inter- and intra-utility has become a critical part of the deregulation picture. Exponential advances in hardware, software, and communication equipment allow the transportation, storing, and manipulation of vast quantities of data at blinding speed relative to just a few years ago. As a result, utilities have shifted their focus to information technology and automation to optimize operations and improve the bottom line. This article proposes a global approach for the management and control of medium-voltage (MV) networks. The efficiency of this approach is analyzed in terms of quality of service, optimization of investment, optimization of installation, maintenance, and simplification of operation.

Power Quality [Book Review]

Abstract: The drive to use electric energy more efficiently has created a need for an increased level in the quality of power supplied to customers. These customers have turned to advances in power electronics to improve the efficiency of their equipment. In many cases, new and more efficient equipment is also more sensitive to power system disturbances. As these devices become more prevalent in commercial and industrial facilities, the number of individuals requiring an understanding of basic power quality increases. Many existing publications address the individual aspects of power quality, such as harmonics, but few exist that attempt to provide an overview of the most common power quality concerns. Those that do exist are written with power quality professionals as their target audience. C. Sankaran’s Power Quality attempts to cover the most common aspects of power quality and do so in such a way as to be informative to those new to, or outside of, the field. In the preface, Sankaran describes the book as “The Power Quality Do-It-Yourself Book.” For the most part, he has succeeded in writing a very good primer on power quality. The first chapter contains definitions of commonly used terms in the power and power quality industries. However, readers should note that his use of the term power frequency disturbance is not part of the standard nomenclature used by the power and power quality communities. He uses the term to describe “low-frequency phenomena that result in voltage sags

Simulation and transient testing of numerical relays

Abstract: ISSN 0895-0156/02/$17.00©2002 IEEE To what extent is the use of transient tests prevalent in the policy of utilities: Acceptance tests Incidence analysis New modular relay definitions Optimal settings Corrective maintenance Relay selection? The main incentive of our research was to tackle the development of diverse tools that, in conjunction, made it possible to establish conclusions to answer this question.