Showing papers in "IEEE Computer Applications in Power in 1994"

Power system applications for phasor measurement units

Abstract: State-of-the-art technology now permits measurement and analysis of power system performance on a scale not previously possible. Synchronized sampling, derived from the GPS (Global Positioning System), and high accuracy sigma-delta analog-to-digital converters form the basis for a system that can measure the state of the power system at a given instant over any area. Samples are acquired 12 times per cycle and are processed by a recursive discrete Fourier transform (DFT) algorithm. This produces the magnitude and angle of the input signal for each sample. The resulting phasors can be combined to produce a positive sequence phasor for a set of three phase inputs. The positive sequence quantities can be used to calculate voltage and current phase and magnitude, real and reactive power, frequency, and impedance. Since the positive sequence parameters are acquired at the same instant (within 1 microsecond), the state of the system at the measured nodes is known at the sample time. Applications to fault recording, disturbance recording, transmission and generation modelling verification, and power system stabiliser testing, are discussed. >

Modern control centers and computer networking

Abstract: The automation of power system operation is generally achieved with the implementation of two control centers, one for the operation of the generation-transmission system and the other for the operation of the distribution system. These control centers are referred to, respectively, as the energy management system (EMS) and the distribution management system (DMS). The EMS may consist of several control centers in a hierarchy. The DMS may be made up of several independent distribution control centers. This article features the fundamental design aspects of modern EMS and DMS control centers (computer networks, distributed processing, and distributed databases), the linking of computer networks, and the communications that support such internetworking. The extension of such networking beyond the confines of system operation to other corporate networks is now made practical by the maturing concepts of client-server architectures and by the availability of modern communication technologies. >

Modern user interface revolutionizes supervisory systems

Abstract: Workstation-based full-graphics technology has fundamentally changed the nature of computerized energy control systems. The proliferation of standards based workstations created an environment that enabled SCADA data to be opened up to an expanded user community within the corporation. Workstation technology has been essential to the emergence of distributed computer system architectures. The existence of UI (user interface) standards has given impetus to independent application specialists to develop products in their chosen area of expertise; the standards have, in effect, created a market for third-party software. This article updates a chapter of the IEEE tutorial 'Fundamentals of Supervisory Systems', which summarized UI architectures and the functionalities typically achieved through the SCADA system's UI facilities. The article briefly describes features of a modern control center's graphical UI and explores some of the ways in which the new technology is being used in everyday operations. >

Real-time monitoring of the TVA power system

Abstract: The Tennessee Valley Authority (TVA) is experimenting with one of the many concepts for the uses of phasor measurements, that of utilizing phasor measurement units (PMUs) as a state estimation system. However, the term state estimation no longer applies; what is being performed is a state determination in near real-time. >

Expert system reasoning streamlines disturbance analysis

Abstract: Houston Lighting & Power funded Texas AM direct interface to the existing digital fault recorder (DFR) system; graphical user interface (GUI) for viewing of results; database management for storing results; and a modem interface to the protection engineer. The system was developed and extensively tested using Electromagnetic Transient Program (EMTP) simulations and actual disturbance records captured by DFRs at various substations. Since then, the system has been connected to a substation DFR for online monitoring of disturbances. This article points out some design and implementation issues and highlights performance validation and operating experience related to the expert system. >

Active DC filter for HVDC systems

Abstract: In pursuit of higher performance and lower cost for harmonic filtering in high-voltage direct current (HVDC) power transmission systems, a prototype of an active DC filter was developed and installed on the DC line at the Lindome converter station of the KontiSkan 2 HVDC link between Sweden and Denmark at the end of 1991. This installation provides practical evidence that an active filter is possible for high voltage transmission systems and that this could be a better and cheaper alternative than the conventional passive filter. The filter is described as is its control and protection. >

GUI display guidelines drive winning SCADA projects

Abstract: This article enumerates the major parameters that should be evaluated at the very beginning of a SCADA/EMS project to choose the most efficient GUI product. Though every customer's needs are different, any GUI system still should have the following chief characteristics: open system approach; seamless interface features; ease of user operation; and acceptability by the operators. >

Voltage flicker measurement and analysis system

Abstract: Electric utilities are faced with the constant challenge of providing a stable and high quality power system with high short circuit capabilities to minimise the effects of fluctuating loads, such as operating large electric furnaces and starting large motors online. One concern is voltage flicker effects on the power system. On-site field tests are useful to verify that voltage flicker is within acceptable limits due to the operation of these fluctuating loads. This article describes the measurement of voltage flicker using a unique flicker measurement and analysis system. The system described in the article is the V-Flicker package. >

Probing power quality data

Abstract: A power quality problem can best be described as any variation in the electric power service resulting in misoperation or failure of end-use equipment. As customers seek to increase utilisation and efficiency, utilities strive to better understand power quality events and their effects on these customers. Utilities are creating special programs and organisations to deal with customer power quality needs. A problem shared by both parties is the need for improved methods in the collection, analysis, and reporting of very large amounts of measured power quality data. This article presents one method currently being used to characterise power quality levels on distribution systems throughout the United States. The method utilises a number of software systems, one of which is the data management and analysis program described in the article. >

Real-time digital simulator for protective relay testing

Abstract: The Western Area Power Administration (WAPA) recognized that real-time testing of protection relays is needed for a full evaluation of different relaying products considered for future use on the WAPA system. In terms of protective relaying, some important sections of the WAPA system have introduced several real challenges in deciding which relaying product will best suit the given application. The relaying applications are quite complex, consisting of parallel lines with series capacitor compensation, MOV protection on the capacitors, and a single-pole reclosing scheme. The authors describe how WAPA implemented a new low-cost, high-performance digital simulator design aimed at providing real-time operation while preserving accuracy and flexibility. >

Distribution automation strategy for the future-changing the momentum

Abstract: Distribution system automation is no longer just an attractive concept. For utilities facing the prospect of a more competitive deregulated environment, it has become a business necessity. Certain forms of distribution control systems were used by electric utilities as early as the 1960s. Both hardware and software have experienced massive improvements, and information technologies and architectures will now support greatly expanded distribution automation. Approaches to utility system management take advantage of the increased cost efficiencies possible with today's improved monitoring and control tools. Programmable meters, packet radios, digital relays, and programmable control devices, such as capacitor controllers, can combine with client-server architectures to create automated systems that are more reliable, and offer a far greater degree of control, even as they reduce operation and maintenance costs. The authors describes how SCE is implementing a program to improve the operational and electrical efficiency of its distribution system, reduce costs, and increase reliability. >

Expert system measures harmonics and EMC

Abstract: The effects of power system harmonics are becoming more and more important as the number of rectifier controlled motors, discharge lamps, and television equipment grows in industrial and utility power systems.The author describes how a modular expert system for measurement and analysis of power system harmonics and electromagnetic compatibility was developed. The system is capable of sampling up to eight channels (either voltage or current) with a sampling frequency of 30 kHz. The measured and digitized values are stored on a hard disk. Discrete Fourier transformation (DFT) analysis may be carried out online for preliminary evaluation and display of the harmonics. This modular, PC-based system may be applied to a variety of industrial and utility electric system analysis tasks, and also used in education. >

DA/DSM directions. An overview of distribution automation and demand-side management with implications of future trends

Abstract: Distribution automation (DA) and demand-side management (DSM) have been the subject of discussion, evaluation, experimentation, and limited implementation for the last 10 to 15 years. At long last, it now appears the power industry is ready to proceed with full-scale implementation. The communication systems seem to be available and affordable, a number of suppliers are offering products specifically designed for the application, and the systems that have been put in place have demonstrated benefits. In addition, the results to date seem to imply a new direction for final implementation, which, for the first time, would offer the possibility of bringing together the complete picture of system operation. Here, the author presents an overview of distribution automation and demand-side management together with implications of future trends. >

Recent advances in master station architecture

Abstract: A new master station architecture, based on the open systems concept, is now widely employed by the industry's vendors and has salient characteristics that can be summarized as follows: industry standard hardware is used to the greatest extent practical; industry standard software is used to the greatest extent practical; a network of computers is accepted as the basic paradigm; configurations exploiting the above characteristics are favored; and configurations based on proprietary hardware are avoided. This article explains why the change occurred, details major characteristics of the new architecture, and speculates on the effects the new architecture will have on the three major industry participants: utilities (buyers) purchasing the systems; contractors (sellers) building the systems; and consultants assisting in system procurement. >

Predicting steady-state instability

Abstract: The ability to know how much load can be met and how much power can be sold while maintaining a safe distance from the point of voltage collapse and steady-state instability is of great concern both in the real-time dispatch and during the operations planning and scheduling activities of power systems. This is particularly true in an increasingly deregulated electric utility industry where power systems are, and will be, dispatched within smaller voltage and steady-state stability margins than in the past. The authors describe a new application of REI-Dimo techniques which targets power system operation close to the maximum power transfer capability while maintaining a safe distance from critical states. >

Managing power system security and optimization

Abstract: PEPCO's new EMS provides unique security and optimization strategies for generation, transmission, and distribution systems via a coordinated suite of real-time closed-loop control functions. The authors discuss the security functions real-time sequence, control hierarchy, optimisation control objectives, contingency-condition optimisation, emergency mode operation, underground transmission network control objectives, radial load bus voltage control objectives, control sequencing, and control execution. >

POWERCOACH-an electricity trading advisor

Abstract: This article presents an overview of the changes taking place in the electric utility industry and goes on to describe the characteristics of existing software packages used in operations planning and the need for a change in the approach to operations planning and management. The article describes a solution for some of the needs emerging in the near term and offers some possibilities for future development paths. EPRI's new PC software applies decision analysis to bulk power transactions, helping electric utilities manage risk and returns in an increasingly complex market. EPRI's goal in creating this tool was to provide a state-of-the-art decision support system to its customers. >

Simulating dynamic interactions of grid-linked wind turbines

Abstract: Models for dynamic interaction of wind turbine generators (WTGs) on electric utility networks have been suggested, but only a few publications have addressed the aggregation of hundreds of turbine generators. This topic has a significant impact on studies related to power system dynamics, because it helps reduce system complexity and computation cost. This article features a study that set out to: simulate the electromechanical dynamics of a typical grid-connected wind turbine generator, test an aggregation technique for representing a group of WTGs by a single unit, and demonstrate how such a complicated analysis of interconnected systems can be performed using state-of-the art software that performs both numerical simulation and linearized eigenstructure studies. The SIMULINK software simplifies the analysis of the interconnected power systems, performing both numerical simulation and linearized eigenstructure studies. >

Demystifying induction motor behavior

Abstract: Induction motors are very simple devices, but, ever since they were introduced by Tesla, they have mystified many practicing engineers. The INSPEC interactive program that runs in Microsoft Windows on 386 or higher PCs, is designed to calculate accurate equivalent circuit models from induction motor standard specifications. It has a full graphical user interface (GUI), created using Microsoft's Visual Basic. The use of the program to examine starting and bus transfer characteristics is discussed. >

Formal techniques improve connectivity in supervisory systems

Abstract: The need to provide communication among the various computers that make up supervisory control and data acquisition (SCADA) systems is encountered more and more frequently. This equipment is usually from various generations, technologies, and manufacturers. Much effort has been made to define a set of standard protocols for both center-remote communications and to center-to-center links of similar or different levels. Nevertheless, the future role of these standards is not clear, and the problem still remains of how to ensure communication among the systems working presently. The authors describe CUP, a protocol conversion tool that enables communication among the multiple components of SCADA systems. CUP is the Spanish equivalent of universal protocol conversion. >

Using control center technology to solve new utility challenges

Abstract: To optimise its diverse resources, Southern Company Services migrated to a distributed client-server architecture, using PCs as clients to prepare data and produce reports and workstations as high-speed servers to store data and perform unit commitment runs. This article discusses this migration project. >

Tailoring SCADA systems for standby power applications

Abstract: Supervisory control and data acquisition (SCADA) systems have been used by the manufacturing and process industries and many electric power utilities for energy management systems, including economic dispatch and the interconnection pricing of energy. However, the use of SCADA in smaller power generation systems is not quite so widespread. This article explains how a SCADA system was custom developed for a standby power generation system recently installed in a commercial office building. >

Automating relay coordination

Abstract: The process of setting relays and checking the coordination between primary and backup relays has always been a time consuming process Automation of various steps of relay setting and checking is easing the tedium of this process for engineers at Consumers Power company This automation is performed by a series of macros written for use with the Computer-Aided Protection Engineering (CAPE) system, which has been featured in previous issues of IEEE Computer Applications in Power and in other technical papers This article illustrates how the functions available in the protection system can be linked together through macros that produce graphical and tabular output that demonstrate the state of coordination between primary and backup relays and other protective devices >

The dream and reality of automated wiring systems

Abstract: To remain competitive in today's business environment, companies must find ways to cut costs without sacrificing the quality of products or services. The Long Island Lighting Company (LILCO) has been able to do just that in the production of wiring diagrams, thanks to a unique PC based CAD software package called Substation/Switchgear Automated Wiring System (SAWS) from Wire Graphics, Inc. The system is not just a drafting tool. It provides the graphic tools necessary to create schematic drawings, wiring diagrams, and associated documentation, and it also allows designers to link the connectivity described in the schematic design with the physical layout of parts on the wiring diagram. This unique feature eliminates the need to manually redraw the connectivity created on the schematics. >

Introducing power monitoring units for distribution networks

Abstract: Power monitoring units are inexpensive devices used to monitor distribution networks. In order to select and maintain power monitoring systems for a distribution network, it is important to understand some basic facts about the devices. This article categorizes power monitoring systems available today and highlights their relative strengths and weaknesses. Inexpensive electronic devices may be installed at customer premises to monitor low-voltage electric supply, using the customer's phone line to communicate with the master station. >

CPC revisited [power system control]

Abstract: For over 20 years, the North American Electric Reliability Council Operating Committee's (NERC-OC) Performance Subcommittee has been using the Control Performance Criteria (CPC) to evaluate the control performance of NERC's control areas. A new, more comprehensive CPC criteria is being put through its trial period by the Performance Subcommittee. The author reviews how the current CPC was developed, implemented, and used to date. >

Load-data access tools cultivate productivity

Abstract: Electric utility load research involves the systematic collection of customers' energy usage by time-of-day, month, season, and year. At many utilities, whole-premise and end-use load data are collected from a large number of customer sites at 15-minute intervals for multiple seasons and even years. Whole premise refers to the total load at a residence, while end-use load may include several individual major appliances, treated separately. As a result, load research data, especially end-use data, is voluminous. Thus, designing a load data distribution system that can respond to data requests in a timely, effective manner is becoming an important planning and operations goal facing many electric utility load research departments. This article discusses how Arizona Public Service Co. (APS) has implemented a load data distribution and access system to improve its staff productivity and communications efficiency. >

Nuclear plants gain integrated information systems

Abstract: Mexico's Laguna Verde nuclear power plant integrated its various systems, making fun use of the existing universe of signals and engineering. This article describes the plant's integrated information system. The development of this system enabled Laguna Verde to fully use the already existing universe of signals and its related engineering during all plant conditions, namely, start up, normal operation, transient analysis, and emergency operation. Integrated systems offer many advantages over segregated systems, and this experience should benefit similar development efforts in other electric power utilities, not only for nuclear but also for other types of generating plants. >

Monitoring power system response to UHP arc furnace operations

Abstract: Electric arc furnaces of the ultra-high-power (UHP) design range have ratings from 20 to over 100 MW. UHP are furnaces, with their large connected loads, are frequently the largest single power consumer in a given section of a power grid. Their operation, therefore, is of serious concern to the power utility. The refiring period at maximum power level is what has been identified as the area of main concern. During this period, the arc tends to cause distortions of the voltage and current waveforms. The combination of the nonlinear arc resistance and the relatively large but linear external reactance results in distortions to the supply voltage at the point of common coupling (PCC). A PC-based data acquisition system has been developed. This was used to measure the voltage and current waveforms at the PCC during various furnace operational modes. From the data acquisition system, the instantaneous and RMS values in the power system were measured at 100000 samples per second and displayed. The operation of a 40 MW arc furnaces at maximum power causes no serious problems on the electric system. However, during the ramping up stage and for loss of a furnace while operating at maximum load, there are measurable changes in the voltage and current profile. >

Migrating resource commitment from mainframe to PC

Abstract: A medium-term unit commitment program is critical to the power operation group of a typical power utility. For the Arizona Public Service Company (APS) this means: a 2-to-5 day study period; up to 40 generators; and up to 20 sales/purchases. The original resource commitment system (RES) was envisioned to run on the real time energy management system computer. For many reasons the package was better suited to the corporate mainframe. As overall corporate computer demand was growing at a faster pace than the capability of the corporate mainframe, so turn-around times for typical RES runs were getting longer. APS decided to move RES to a PC platform. To accomplish this, the decision was made to migrate to an OS/2 platform using IBM PS/2, some 80286 and some 80486 based, connected using an Ethernet local area network. The new RES program, the user interface, the conversion of the source code to C, and the conversion of the database are discussed. >