This article looks at the various applications of digital simulator technology that have been used to meet the testing requirements of today's more advanced power system protection relays. The authors describe how digital simulators present a new development tool for real-time simulation techniques and for the automation of protective relay testing.

Voltage sags are momentary dips in voltage that may cause misoperations to the electric utility customers' sensitive loads. These misoperations may only be an annoyance to the residential sector, but, on the industrial and commercial front, they can cost millions of dollars each year. It is impossible to eliminate all of these faults and associated voltage sags, but an improvement can be achieved through power system modifications on both the utility system and the industrial or commercial power system. The evaluation of these system modifications was difficult in the past, but the authors describe a voltage sag analysis program, developed by Power Technologies, Inc., which has simplified the task. The program uses methodologies developed for the update of the IEEE Gold Book (IEEE Standard 493, Recommended Practice for the Design of Reliable industrial and Commercial Power Systems). The results of this sag analysis program form the basis of possible future cost-benefit analysis enabling electric utilities and utility customers to make the most economic system modification.

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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. >

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Utilities and consultants with an in-depth knowledge and tradition of conducting power system operation performance and optimization studies have frequently requested adequate and accurate procedures and tools to tackle this special field of power system analysis appropriately. This need to solve complex operation analysis and special component planning problems has prompted the development of adequate methods and tools at DIgSILENT Systems in cooperation with FICHTNER C.E. This article focuses on various possibilities to approach this problem and reports on the applied strategies and methods. Comprehensive examples are given to demonstrate the capabilities of the implemented procedures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>