Showing papers in "IEEE Computer Applications in Power in 1995"

Optimization applications to power distribution

Abstract: An electric utility's power distribution system can account for up to 60 percent of capital budget and 20 percent of operating costs, making it a significant expense. Minimizing the cost of the distribution system can be a considerable challenge, as the feeder system associated with only a single substation may present a distribution designer with thousands of feasible design options from which to choose. Finding the overall least-cost plan for the distribution system associated with several neighboring substations can be a truly daunting task. For these reasons, the use of computer-aided tools that help identify the lowest cost distribution configuration has been a focus of much R&D work in the last 3 decades, producing a number of computerized optimization programs that can be viewed from the user's standpoint as tools to help find the best design from among those many possibilities. >

GUI enhances electromagnetic transients simulation tools

Abstract: The authors discuss the use of a graphical user interfaces (GUIs) for power system EM transients programs. GUIs increase productivity by enabling swift assembly of circuits, fast interactive simulations, and quick and easy analysis of results. The authors discuss the preparation of data files, running the simulation, analysis and documentation of the results, and the simulation program. >

Fault location using digital relay data

Abstract: The most accurate and reliable fault location results are obtained using new algorithms that consider the fault data from both ends of the line together. Obviously, the data from the two ends must be brought together via data communications, either from one substation to the other or to a computer at a third site to which both substations can send the data. This might be a control center, relay engineer's office, or maintenance depot, which are ideal locations for really accurate fault location displays to be presented. Some two-ended location algorithms require time synchronization of the data from the two ends, which is not widely available. This article presents new calculations that do not require any such synchronization of the records to achieve excellent accuracy. Following an overview of the technical problems in computing fault location from fault voltage and current signals, a sampling of the newest and most accurate techniques that are easily implemented in existing digital devices for calculating location from one-ended or two ended line fault data records is given. >

Spatial load forecasting

Abstract: The reliability, efficiency, and economy of a power delivery system depend mainly on how well its substations, transmission lines, and distribution feeders are located within the utility service area, and how well their capacities match power needs in their respective localities. Often, utility planners are forced to commit to sites, rights of way, and equipment capacities years in advance. A necessary element of effective expansion planning is a forecast of where and how much demand must be served by the future T&D system, a forecast with sufficient accuracy and detail to allow meaningful determination of sites and sizes for future substation, transmission, and distribution facilities. The authors give a brief history of small area load forecasting and then describe spatial load forecasting techniques. The three-stage method forecasts with accuracy and detail, allowing meaningful determination of sites and sizes for future substation, transmission, and distribution facilities. >

Impact of market restructuring on power systems operation

Abstract: What effect will competitive pricing have on control center applications, information technology requirements, and transaction analysis? The move toward market-based pricing places significant new requirements on the utility's technological infrastructure. Information systems and control center applications and procedures are all affected, albeit to varying degrees. A few examples of affected functions are bidding procedures, ancillary services, and financial hedging contracts. This article has outlined some of the changes that may be coming to the Electricity Supply Industry in the United States as it moves to one which makes more use of marginal pricing concepts. In many respects, the major changes are changes in mind set and procedures. Many of the control and analysis tools will remain the same. >

High fidelity simulation of power system dynamics

Abstract: Detailed assessment of phenomena occurring in a power system remains a major challenge for most utilities. Complex simulations often involve fast and slow phenomena, both of which must be taken into account to obtain a faithful representation of reality. Methods that consist of splitting these phenomena into different classes (transient, mid-, or long-term stability), each corresponding to specialized software and a particular model, are no longer satisfactory. To meet this challenge, EUROSTAG software was developed for the simulation of power system dynamics. It covers the full range of phenomena, from transient to long-term stability, using a single power system model, and its application field is extensive: from the electromechanical oscillations up to the daily load evolution; from the line tripping to the centralized frequency or voltage control; from the generalized blackout to the system restoration procedure; and from tuning the generating unit controller to studying power electronics such as FACTS or HVDC. Thanks to an automatically variable step-size strategy, this single integrated program with single and extended modeling simulates the whole set of phenomena with a high degree of accuracy. Great attention has been paid to user-friendliness. Users are able to design their own process models and build new scenarios interactively, conveniently, and rapidly. >

Hands-on teaching of power system dynamics

Abstract: Knowledge of power system dynamics is essential for any engineer who is to design or operate a modern interconnected power system System instability and, in the extreme, system collapse are very costly to power utilities and their customers Power system dynamics is not an easy subject to teach What is required is a hands-on computer course in which students can work on simplified but, at the same time, realistic models of the power system This article features a power system analysis and design package for use in hands-on teaching of power system dynamics >

Advanced SCADA concepts

Abstract: The typical utility system planner faces a wide variety of concepts and applications to consider when procuring a supervisory control and data acquisition (SCADA) system. The system's performance requirements are influenced by an arena of rapidly advancing technologies and a highly competitive business environment. Unlike other elements of the electric utility industry, these changes are not evolving specifically for the SCADA industry; they are being driven by other technology forums, with a profound impact on the SCADA system of the future. This article explores some of these concepts and suggests technology and business issues to consider when planning for the SCADA system of tomorrow. In particular the authors discuss the application of SCADA technology to a fully integrated substation system. They discuss substation controllers, substation design and operation, the substation protection interface, and the substation information system. >

Integrated approach to transfer limit calculations

Abstract: Operators and planners of transmission systems must deal with new concerns brought about by open access to the transmission grid and an increase in the number of power wheeling transactions. This problem is compounded by additional regulatory and environmental concerns that have limited the amount of new transmission facilities that have been constructed in recent years. As a result, the question of how much additional power can be safely wheeled across a system has taken on new urgency. In addition, the requirements and methods for calculating transfer limits have evolved from an early emphasis on overload (using linear DC load-flow models) and transient stability limits to include voltage and voltage stability limitations. Utilities typically apply different methods and computer programs to determine transfer limits caused by each failure phenomenon. The various limit reports must then be consolidated in a time-consuming process. This article presents an integrated method for determining the transfer limits on a specified transmission interface due to low voltage, voltage collapse, and thermal overload constraints resulting from branch outages. >

ANNs pinpoint underground distribution faults

Abstract: Online fault location in underground power distribution networks that involve interconnected lines (cables) and multiterminal sources continues to receive great attention, with limited success in techniques that would provide simple and practical solutions. This article features a new online fault location technique that: uses the pattern recognition feature of artificial neural networks (ANNs); and utilizes new capabilities of modern protective relaying hardware. The output of the neural network can be graphically displayed as a simple three-dimensional chart that can provide an operator with an instantaneous indication of the location of the fault. >

Synchronized sampling improves fault location

Abstract: Transmission line faults must be located accurately to allow maintenance crews to arrive at the scene and repair the faulted section as soon as possible. Rugged terrain and geographical layout cause some sections of power transmission lines to be difficult to reach. Therefore, robustness of the accurate fault location determination under a variety of power system operating constraints and fault conditions is an important requirement. This article introduces a unique concept of high-speed fault location that can be implemented either as a simple add-on to the digital fault recorders (DFRs) or as a stand-alone new relaying function. This advanced concept is based on the use of voltage and current samples that are synchronously taken at both ends of a transmission line. This sampling technique can be made readily available in some new DFR designs incorporating receivers for accurate sampling clock synchronization using the satellite Global Positioning System (GPS). >

Exercise the power of the World Wide Web

Abstract: The World Wide Web is a hypertext-based, platform-independent means of displaying text, graphic, audio, and video information over the Internet. Twenty million people now use the Internet, and the number of World Wide Web sites is well over one million and growing rapidly. Web sites are available all over the world, although most are located in the United States. Importantly, the Web's design is consistent with many of our information gathering instincts. It encourages browsing and experimentation and allows each person at computer sites around the world to design unique ways to present and use information. The author discusses its practical applications, explains how hypertext works, and discusses how it is can be used by power utilities. Reserving a password and gaining access to the World Wide Web are also discussed. >

Signatures and software find high impedance faults

Abstract: The detection of high-impedance faults on electrical distribution systems has been one of the most persistent and difficult problems facing the electric utility industry. High-impedance faults result from the unwanted contact of a primary circuit conductor with objects or surfaces that limit the current to levels below the detection thresholds of conventional protection devices. The author describes how recent advances in digital technology have enabled a practical solution for the detection of a high percentage of these previously undetectable faults. >

Distribution engineering tool features a flexible framework

Abstract: The Electric Power Research Institute (EPRI) has been involved in developing a software package designed to meet the needs of distribution engineers. The result of these efforts is a workstation software package (DEWorkstation) that provides an open architecture environment with integrated data and applications. Analysis, design, and operation modules access database data and exchange data through common functions. The open architecture allows external application modules to be added to the workstation. External measurements such as voltage, current, and temperature may be imported and displayed on the circuit schematic. These imported variables are made available to any application program running within the workstation. This distribution engineering tool is designed to meet the analysis, planning, design, and operation needs of distribution engineering through its available application modules. Modules perform the following types of analyses: power flow, load estimation, line impedance calculation, fault analysis, capacitor placement, phase balancing, and more. External data such as customer information system data and distribution transformer data may be imported. The workstation is designed to provide utilities with a platform suitable for distribution automation evaluations. >

Object oriented expert system estimates line ampacity

Abstract: In a competitive power supply business environment, line ampacity predictions are required by electric power utilities for economic generation planning, system dispatching, contingency planning, security analysis, and for normal and emergency operation of electric power systems. The line ampacity system featured in this article calculates ampacity from general purpose National Weather Service (NWS) forecasts and does not require additional hardware on power lines. By designing the ampacity expert system with objects and rules, it can be easily implemented in small and large electric companies. The Line Ampacity System (LINEAMPS) is a PC/Windows-based, power-line ampacity, expert-system program for the estimation of line ampacity during steady-state, dynamic state, and transient conditions. It was developed by the application of artificial intelligence using object-oriented, knowledge-base design of the power line environment. The expert system provides hourly values of line ampacity up to 7 days in advance and is used for the operation, planning, and design of transmission and distribution lines at all voltages. >

Control area trends: principles and responses

Abstract: The control of interconnected power system operations is being affected by the consolidation of control areas and the introduction of new control areas. Computers and communication networks are the tools used to turn the momentum of these two trends to the advantage of the industry. Better system control and improved system security can be the result if there is productive cooperation, commitment, communication, and control by the interested parties who must establish the parameters for future system control and operations. The principles and techniques of this cooperation are discussed. >

Virtual instrument measures harmonic filter duty

Abstract: Harmonic filters for a static VAr compensator (SVC) suppress power frequency harmonics generated by the nonlinear characteristic of the thyristor controlled reactors and electric arc furnace loads. SVC filters also provide the 60 Hz capacitive current needed by the SVC to reduce bus voltage flicker. Following reactor and capacitor failures the reliability of the SVC filter was improved. The first step was to measure the SVC filter stresses which was performed using a virtual instrument. The measurement equipment consisted of a personal computer equipped with two analog-to-digital (4/D) input boards, two signal conditioning input boards, and commercially available instrument and control software capable of configuring these basic hardware components for user defined instrumentation and analysis. Virtual instruments were used to sample, store, analyze, and display 32 channels of high speed data for 55 minutes of the combined furnace heat cycle. The author discusses the virtual instrument software, measurement and analysis technique, and statistical analysis. >

Synchronized, end-to-end tests on protective relay schemes

Abstract: Public domain satellite timing signals are being used to synchronize simultaneous secondary injection tests on power system protective relay schemes at remote ends of power transmission lines. By this means, protection schemes that include communication functions can be tested in a meaningful, time-related manner. A discussion of the need for such a test method, the principles and history of the test method, and details of a recent series of tests are included. >

Reap the rewards of quality with ISO 9000

Abstract: ISO 9000 is a series of international standards for quality management systems. It establishes the organizational structure and processes for assuring that the production of goods or services meet a consistent and agreed-upon level of quality for a company's customers. Whether or not a company decides to seek ISO 9000 certification, implementing such discipline can achieve greater quality and efficiency. This article describes the principles of the ISO 9000 series of standards, which are interpreted by ISO 9000-3 to software development and maintenance. It covers the following topics: an overview of ISO 9000 series standards; the registration process; the twenty clauses of ISO 9001; and implementation of ISO 9000 for software development and maintenance. >

Relay database design

Abstract: Many electric utilities use computer databases to store their relay data. The database naturally gives access to many users, coordinates modifications, and generates the necessary reports for different purposes. The relay database must accommodate a wide variety of protective devices. Users of a relay database include relay engineers, relay technicians, system operators, and other field personnel. Information wanted by these users takes the form of setting sheets, test forms, and substation reports. We conducted an informal survey of relay databases in use at different utilities and found that the readability of the forms and reports varies greatly from one database to another. The term readability here refers to the ease with which the relay information can be viewed and updated by humans and by computer programs. The readability and effectiveness of a relay database hinge on the underlying data organization. This article describes several existing relay database designs and their advantages and disadvantages, and features a new database model that has proven to be flexible and easy to use and can accommodate a wide variety of relay types. >

Internetworking with the Power Globe remailer

Abstract: The use of the Internet by power engineers has been growing rapidly. The most common use is person-to-person electronic mail (E-mail), which is beginning to replace long-distance phone calls in many instances. Power engineers in academia have long been using E-mail to communicate with each other on research and educational matters. With utilities, vendors, and consultants joining the Internet in increasing numbers, the power industry is making more use of E-mail for business communications. In addition to person-to-person E-mail, it is possible to send one-to-many broadcast E-mail messages over the Internet. Electronic mailing lists are one way of broadcasting messages. An Internet remailer is an E-mail address to which messages may be sent for the purpose of broadcasting to all people whose E-mail addresses are in the remailer's list. This article describes a remailer that has been serving power engineers for the past few years, explains the functions of the list, and provides thoughts on its future based on the experience gained so far. The goal is to inform the power engineering community at large, especially those in the power industry, of its existence and to invite power engineers to add their names to the Power Globe mailing list. >

Investigating DSM cost and benefit options

Abstract: For the decentralized assessment of demand side management (DSM) options, a practical set of instruments called GOLDSMITH (an acronym for Groningen system for the evaluation of options for load and demand-side management by interactive testing of modifications of hourly load shapes) was developed that can be used to confront tentative ideas and plans with empirical data. These instruments contain some original ideas concerning DSM modeling. Application of such instruments can help users develop their ideas, offer a test bed for DSM options, and strengthen the relation between theory, ideas, and the empirical facts concerning energy management issues. Initially, the project's main result was seen as a decision-support system that uses a knowledge base about DSM options. Rules would be applied to this knowledge base, or structure would transform the options database into a larger system. Consultation of the expert system would lead to pertinent conclusions about the viability of DSM options. However, this initial goal evolved during the course of the research to an approach that reinstated the operator of the software as the final decision-maker and expert. This article describes directions taken during the research venture, the investigative software tools spawned by the research, and some practical applications. >

A system operator's view of evolving applications

Abstract: Digital-computer applications to power system operation allow system operators to manage their increasingly complex systems with increased efficiency and reliability. This article takes the perspective of one power system operator who was fortunate to have been involved in the design, construction, and operation of four generations of operating centers, and who witnessed the evolution of electric system control from limited manual methods to sophisticated system operation management facilities. >

Short-circuit simulations help quantify wheeling flow

Abstract: New England transmission system owners use the results from short-circuit simulations to quantify the transmission wheeling services they provide to deliver power from the Connecticut, Maine, and Vermont Yankee Nuclear Power Plants. The wheeling service of a transmitting utility, defined in terms of MW-miles, is determined with the use of fault currents to reflect the flow of MW entitlements over the New England transmission system. The use of commercially available software to automate simulations, perform the MW-miles calculation, and tabulate the results significantly reduces the time and computational effort. >

Forecasting supply and demand with reliable facts and figures

Abstract: One activity of the North American Electric Reliability Council (NERC) is the annual compilation of electric utilities' forecast relating to electricity supply and demand. The author describe how this data is available to the industry in a database and software package known as ES&D, which provides data in a concise and useful format to satisfy the needs of a wide variety of industry audiences. From the mid-1970s to 1993, ES&D was published as a printed report. Since 1994, it has been published only in electronic format, with each publication including the current forecast data set and the four most recent data sets. >

Digital models simulate physical test facilities [power systems]

Abstract: Since electric power systems first went into commercial operation, there has been a need to model the performance of power system equipment so that design engineers could minimize unexpected problems. For transient analysis, digital techniques offer flexibility in hardware, software, and model development. Here, the authors describe how, in order to validate such models, physical laboratory tests must be performed on actual apparatus and compared with their digital counterparts. >

Integrating third party packages into an EMS

Abstract: The authors describe how the use of third-party software packages in a vendor's SCADA/EMS offers electric utilities flexibility in obtaining solutions that best fit their specific needs. However, the use of third-party packages also raises several major issues, such as acceptance by the end user, the use of standards and guidelines, interfaces, system security, software and hardware maintenance/upgrades, and training. This article describes the authors' approach to the integration of these diverse third-party packages and highlights the merits and pitfalls associated with such integration. In addition, they ruminate on the lessons learned from this experience and propose some guidelines for electric utilities embarking on similar ventures. >

Gateway system integrates multiserver/multiclient structure

Abstract: The integration of a new energy management system (EMS) center into Hydro-Quebec's existing EMS has imposed major changes on its telecommunications environment, including modifications to the existing remote terminal units (RTUs) in its regional SCADA centers. The authors describe how, in order to integrate the different generations of technology, a transputer-based multiserver/multiclient gateway system was designed. The system is characterized by its relatively low cost, powerful processing capacity and compact size. >

Routing SCADA data through an enterprise WAN

Abstract: Houston Lighting and Power (HLandP) and many other large utilities have invested substantial resources in developing integrated enterprise wide area networks (WANs). The WAN provides unprecedented opportunities for integrating information throughout the corporation, resulting in improved efficiency and reduced costs of operation. In contrast, present dedicated point-to-point SCADA data circuits from the energy management system (EMS) to remote terminal units (RTUs) are not currently integrated with the network, nor replicated in any offsite backup system. An integrated approach might integrate communications from selected RTUs over the WAN to a backup system or the EMS. Such an approach would potentially provide improved disaster recovery, more efficient use of communications, reduced maintenance costs, and improved availability of operational data. RTU data, however, is fundamentally different from most other WAN traffic in that it is critical to the moment-to-moment operation of the utility and consists of a large number of messages repeated frequently and continuously. There are valid concerns as to whether the stability, availability, and inherent latency of the WAN would be adequate to support operations of a backup or primary SCADA system. There are also concerns about the adverse effects that SCADA traffic might have on the WAN. These concerns led to the project featured in this article, which tested the operational suitability and effectiveness of routing SCADA data between selected RTUs and a central site on the WAN. >

Engineering analysis takes an interactive view

Abstract: V-GRAPH, a one-line diagram and database program described in this article, is a Windows-based graphical interface to a comprehensive power system database. The database is common to individual power system modeling programs. Users need not enter data for separate applications. The capabilities of this graphical interface, which include one-line diagram drawing, data entry via click-on devices, database storage and graphical display of engineering analysis results, are attuned to the current trend towards visual data entry. The program runs under Microsoft Windows Version 3.1 and higher, on IBM-PCs or compatibles, and requires a Windows compatible mouse. >