Electromechanical oscillations are inherent to interconnected power systems. However, the frequency of the oscillations and the number of generators that oscillate in any electromechanical oscillatory mode depend on the structure of the power system network. Low frequency electromechanical oscillations occur when existing generation/load areas are connected to other similar areas by relatively weak transmission lines. Weak interconnections are obvious in many interconnected systems, for example, when two independent electric grids are interconnected for the first time through one or two tie lines. However, in systems that have been interconnected for some time, such as the US/Canadian interconnected systems, and that are being stressed by increased load, weak links are less obvious. Often, the first signs of trouble are low frequency oscillations becoming unstable. The connection between loading and stability is not always obvious. It is also unclear which contingencies may lead to oscillatory instability. This tutorial examines in detail the relationship between low frequency oscillations and weak interconnections in the transmission system network. The basis of the analysis is the observation that generators in specific areas of a power system behave coherently in low frequency oscillations and that groups of coherent generators are separated from other groups of coherent generators by weak interconnections. This observation is also the starting point for dynamic system reduction.
{"title":"Power system structure and oscillations","authors":"G. Rogers","doi":"10.1109/67.755641","DOIUrl":"https://doi.org/10.1109/67.755641","url":null,"abstract":"Electromechanical oscillations are inherent to interconnected power systems. However, the frequency of the oscillations and the number of generators that oscillate in any electromechanical oscillatory mode depend on the structure of the power system network. Low frequency electromechanical oscillations occur when existing generation/load areas are connected to other similar areas by relatively weak transmission lines. Weak interconnections are obvious in many interconnected systems, for example, when two independent electric grids are interconnected for the first time through one or two tie lines. However, in systems that have been interconnected for some time, such as the US/Canadian interconnected systems, and that are being stressed by increased load, weak links are less obvious. Often, the first signs of trouble are low frequency oscillations becoming unstable. The connection between loading and stability is not always obvious. It is also unclear which contingencies may lead to oscillatory instability. This tutorial examines in detail the relationship between low frequency oscillations and weak interconnections in the transmission system network. The basis of the analysis is the observation that generators in specific areas of a power system behave coherently in low frequency oscillations and that groups of coherent generators are separated from other groups of coherent generators by weak interconnections. This observation is also the starting point for dynamic system reduction.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"236 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123295631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fuzzy logic controllers are rapidly becoming a viable alternative for classical controllers. The reason for this is that a fuzzy controller can imitate human control processes closely. Fuzzy logic technology enables the use of engineering experience and experimental results in designing an embedded system. In many applications, this circumvents the use of rigorous mathematical modeling to derive a control solution. Another advantage of fuzzy logic control is that it allows for a model-free estimation of the system. In other words, the designer does not need to state how the outputs depend mathematically upon the inputs. A fuzzy controller can be developed by encoding the structured knowledge of the system, which will allow faster control algorithms to be developed in less time and at less cost. With the advance of microprocessors and digital signal processors (DSPs), fuzzy logic control techniques are becoming more attractive for real-time control problems. It is expected that it will be implemented in many power system control applications in the near future. The paper describes a fuzzy logic based closed loop control system which controls the armature voltage of a generator by varying its field current in real-time.
{"title":"Fuzzy logic based voltage controller for a synchronous generator","authors":"B. Lameres, M. H. Nehrir","doi":"10.1109/67.755646","DOIUrl":"https://doi.org/10.1109/67.755646","url":null,"abstract":"Fuzzy logic controllers are rapidly becoming a viable alternative for classical controllers. The reason for this is that a fuzzy controller can imitate human control processes closely. Fuzzy logic technology enables the use of engineering experience and experimental results in designing an embedded system. In many applications, this circumvents the use of rigorous mathematical modeling to derive a control solution. Another advantage of fuzzy logic control is that it allows for a model-free estimation of the system. In other words, the designer does not need to state how the outputs depend mathematically upon the inputs. A fuzzy controller can be developed by encoding the structured knowledge of the system, which will allow faster control algorithms to be developed in less time and at less cost. With the advance of microprocessors and digital signal processors (DSPs), fuzzy logic control techniques are becoming more attractive for real-time control problems. It is expected that it will be implemented in many power system control applications in the near future. The paper describes a fuzzy logic based closed loop control system which controls the armature voltage of a generator by varying its field current in real-time.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128958205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Information management technology has undergone tremendous change over the course of the last decade. Exponential advances in hardware, software and communication equipment allow the transportation, storage and manipulation of vast quantities of data at blinding speed relative to just a few years ago. The phenomenal growth of the Internet has delivered unprecedented access to data virtually independent of distance or location. Although these enabling technologies have reached far into work and home environments, they have as yet been little utilized within substations. This article examines what is required to introduce information management technology to the substation and how to turn a substation into a distributed database server.
{"title":"How to turn a substation into a database server","authors":"D. Proudfoot, D. Taylor","doi":"10.1109/67.755643","DOIUrl":"https://doi.org/10.1109/67.755643","url":null,"abstract":"Information management technology has undergone tremendous change over the course of the last decade. Exponential advances in hardware, software and communication equipment allow the transportation, storage and manipulation of vast quantities of data at blinding speed relative to just a few years ago. The phenomenal growth of the Internet has delivered unprecedented access to data virtually independent of distance or location. Although these enabling technologies have reached far into work and home environments, they have as yet been little utilized within substations. This article examines what is required to introduce information management technology to the substation and how to turn a substation into a distributed database server.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131545437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The insertion of dispersed generation into existing electric power systems has a great impact on real-time operation and planning. Several uncertainties characterize the ability of the existing power system to integrate this form of generation, Hence, dispersed generation must be taken into consideration in power system performance so that operation and security are not disturbed. Dispersed generation increases the complexity of controlling, protecting and maintaining power distribution systems. This article focuses on some technical aspects, but not on the impact on the quality of supply and on tariff signals.
{"title":"Dispersed generation impact on distribution networks","authors":"N. Hadjsaid, Jerseyman Canard, F. Dumas","doi":"10.1109/67.755642","DOIUrl":"https://doi.org/10.1109/67.755642","url":null,"abstract":"The insertion of dispersed generation into existing electric power systems has a great impact on real-time operation and planning. Several uncertainties characterize the ability of the existing power system to integrate this form of generation, Hence, dispersed generation must be taken into consideration in power system performance so that operation and security are not disturbed. Dispersed generation increases the complexity of controlling, protecting and maintaining power distribution systems. This article focuses on some technical aspects, but not on the impact on the quality of supply and on tariff signals.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127261233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. McCalley, V. Ajjarapu, J. D. L. Ree, A. Phadke, G. Sheblé, S. Venkata, V. Vittal
The PowerLearn approach to power engineering education is under development by a core group of faculty and students at Iowa State University (ISU) and Virginia Tech (VT), under funding from the National Science Foundation (NSF) and the Electric Power Research Institute (EPRI). Four basic features characterize the approach. Courseware modularity provides that the material is organized by topic rather than by course. A Web site provides module storage and dissemination. Interactive visualization and simulation tools are heavily used in module construction. In addition, this project is integrated with efforts at both schools to develop new introductory undergraduate courses in electric power engineering. These courses serve well to illustrate the modular approach to course design.
{"title":"Multimedia courseware sparks interest in the industry","authors":"J. McCalley, V. Ajjarapu, J. D. L. Ree, A. Phadke, G. Sheblé, S. Venkata, V. Vittal","doi":"10.1109/67.721700","DOIUrl":"https://doi.org/10.1109/67.721700","url":null,"abstract":"The PowerLearn approach to power engineering education is under development by a core group of faculty and students at Iowa State University (ISU) and Virginia Tech (VT), under funding from the National Science Foundation (NSF) and the Electric Power Research Institute (EPRI). Four basic features characterize the approach. Courseware modularity provides that the material is organized by topic rather than by course. A Web site provides module storage and dissemination. Interactive visualization and simulation tools are heavily used in module construction. In addition, this project is integrated with efforts at both schools to develop new introductory undergraduate courses in electric power engineering. These courses serve well to illustrate the modular approach to course design.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124576730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Artificial neural networks have been applied to power systems in such areas as control, load forecasting, monitoring, diagnosis, and analysis. Their prevalence in the literature and product lines of the electric utility industry has almost overworked the descriptor "intelligent". However, ANNs do not have an IQ. They exhibit attributes that humans often associate with intelligence: an ability to learn, to communicate, to perceive, or to reason. The objective of this tutorial is to give a basic understanding of ANNs and computational intelligence. This is accomplished by discussing the historical and biological basis of ANNs and reviewing two representative architectures from a simple taxonomy for ANNs. In this tutorial, the use of the term architecture is used to imply both a network topology and a learning rule. Resources for further studies and free software are also recommended.
{"title":"Artificial neural networks and computational intelligence","authors":"R. King","doi":"10.1109/67.721699","DOIUrl":"https://doi.org/10.1109/67.721699","url":null,"abstract":"Artificial neural networks have been applied to power systems in such areas as control, load forecasting, monitoring, diagnosis, and analysis. Their prevalence in the literature and product lines of the electric utility industry has almost overworked the descriptor \"intelligent\". However, ANNs do not have an IQ. They exhibit attributes that humans often associate with intelligence: an ability to learn, to communicate, to perceive, or to reason. The objective of this tutorial is to give a basic understanding of ANNs and computational intelligence. This is accomplished by discussing the historical and biological basis of ANNs and reviewing two representative architectures from a simple taxonomy for ANNs. In this tutorial, the use of the term architecture is used to imply both a network topology and a learning rule. Resources for further studies and free software are also recommended.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127206357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An optical wide-area network (WAN) system was designed to permit and integrate control over a power transmission network that stretches over a large geographical area in the Kingdom of Saudi Arabia. This integration will monitor the output of power plants and substations in various regions and will allow for the linking of regional dispatch load centers. The design scheme employs SCADA subsystems and consists of multiple client-server architectures with optical links in ring and bus topologies as ground or aerial cables. The system is proposed around an existing large power grid with real parameters and attributes indicated. WANs are necessary for global power networks to achieve system management as well as control of complex situations, such as load variations within the network regions or protective relaying of power links.
{"title":"Optical nets integrate control over global grids","authors":"A. Adas","doi":"10.1109/67.721705","DOIUrl":"https://doi.org/10.1109/67.721705","url":null,"abstract":"An optical wide-area network (WAN) system was designed to permit and integrate control over a power transmission network that stretches over a large geographical area in the Kingdom of Saudi Arabia. This integration will monitor the output of power plants and substations in various regions and will allow for the linking of regional dispatch load centers. The design scheme employs SCADA subsystems and consists of multiple client-server architectures with optical links in ring and bus topologies as ground or aerial cables. The system is proposed around an existing large power grid with real parameters and attributes indicated. WANs are necessary for global power networks to achieve system management as well as control of complex situations, such as load variations within the network regions or protective relaying of power links.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126202753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Hatziargyriou, J. Jaszczyński, G. Atsaves, D. Agoris
Graphical user interfaces (GUI) provide interactive and intuitive visual communication to power system analysis application programs, enhancing the capabilities of engineers to conduct studies with ease and flexibility. As a result, since the late 1970s, a number of interactive graphical packages for power system analysis have been developed and are in widespread use. Object-oriented programming is gaining popularity, while the Windows environment is assuming a growing role in PC hardware platforms, due to its increased capabilities as a GUI environment. There are many different graphical packages for simulating, analyzing, and teaching power systems operations (built using such programming tools as C++, Object Pascal for Windows, or Visual Basic) that are the results of implementing object-oriented methodology in creating graphical user interfaces. This article focuses on possibilities offered by rapid application development (RAD) tools in building graphical user interfaces for Windows 3.X, Windows 95, and Windows NT platforms. RAD is a new way of programming that allows an application to be built interactively.
{"title":"Building GUIs for interactive network analysis","authors":"N. Hatziargyriou, J. Jaszczyński, G. Atsaves, D. Agoris","doi":"10.1109/67.721703","DOIUrl":"https://doi.org/10.1109/67.721703","url":null,"abstract":"Graphical user interfaces (GUI) provide interactive and intuitive visual communication to power system analysis application programs, enhancing the capabilities of engineers to conduct studies with ease and flexibility. As a result, since the late 1970s, a number of interactive graphical packages for power system analysis have been developed and are in widespread use. Object-oriented programming is gaining popularity, while the Windows environment is assuming a growing role in PC hardware platforms, due to its increased capabilities as a GUI environment. There are many different graphical packages for simulating, analyzing, and teaching power systems operations (built using such programming tools as C++, Object Pascal for Windows, or Visual Basic) that are the results of implementing object-oriented methodology in creating graphical user interfaces. This article focuses on possibilities offered by rapid application development (RAD) tools in building graphical user interfaces for Windows 3.X, Windows 95, and Windows NT platforms. RAD is a new way of programming that allows an application to be built interactively.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"150 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131660321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High demands are imposed on power transformer protective relays. Requirements include dependability (no missing operations), security (no false trippings), and speed of operation (short fault clearing time). The operating conditions of power transformers do not make the relaying task easy. Protection of large power transformers is one of the most challenging problems in the power system relaying area. Advanced digital signal processing techniques and artificial intelligence (Al) approaches to power system protection provide the means to enhance the classical protection principles and facilitate faster, more secure, and dependable protection for power transformers. Also, it is anticipated that, in the near future, more measurements will be available to transformer relays, owing to both substation integration and novel sensors installed on power transformers. All of this will change the practice for power transformer protection. This article briefly reviews the state of the art, but is primarily devoted to discussion of new approaches and future directions in digital relaying for power transformers.
{"title":"Digital relays improve protection of large transformers","authors":"B. Kasztenny, M. Kezunovic","doi":"10.1109/67.721702","DOIUrl":"https://doi.org/10.1109/67.721702","url":null,"abstract":"High demands are imposed on power transformer protective relays. Requirements include dependability (no missing operations), security (no false trippings), and speed of operation (short fault clearing time). The operating conditions of power transformers do not make the relaying task easy. Protection of large power transformers is one of the most challenging problems in the power system relaying area. Advanced digital signal processing techniques and artificial intelligence (Al) approaches to power system protection provide the means to enhance the classical protection principles and facilitate faster, more secure, and dependable protection for power transformers. Also, it is anticipated that, in the near future, more measurements will be available to transformer relays, owing to both substation integration and novel sensors installed on power transformers. All of this will change the practice for power transformer protection. This article briefly reviews the state of the art, but is primarily devoted to discussion of new approaches and future directions in digital relaying for power transformers.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115164370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
While research and development work in the area of microprocessor-based relays continues with fervent interest, relay modeling plays a significant role in performance evaluation of new and existing designs and for performing a variety of studies. At the University of Saskatchewan, researchers are implementing a variety of new relay designs using general-purpose hardware. The functions of a microprocessor-based relay are software controlled, so it is conceivable to change a relay's protection function by simply replacing the installed software. In this context, it is possible to contemplate the development of a generalized modeling technique for generating a software model for any microprocessor-based relay implemented using the general-purpose hardware. A modeling package has been developed for generating models of relays. These models can be used for performing a variety of protection and system studies, and they also serve as valuable educational tools. The authors describe the package and its implementation.
{"title":"Generating relay models for protection studies","authors":"T. Sidhu, M. Hfuda, M. Sachdev","doi":"10.1109/67.721701","DOIUrl":"https://doi.org/10.1109/67.721701","url":null,"abstract":"While research and development work in the area of microprocessor-based relays continues with fervent interest, relay modeling plays a significant role in performance evaluation of new and existing designs and for performing a variety of studies. At the University of Saskatchewan, researchers are implementing a variety of new relay designs using general-purpose hardware. The functions of a microprocessor-based relay are software controlled, so it is conceivable to change a relay's protection function by simply replacing the installed software. In this context, it is possible to contemplate the development of a generalized modeling technique for generating a software model for any microprocessor-based relay implemented using the general-purpose hardware. A modeling package has been developed for generating models of relays. These models can be used for performing a variety of protection and system studies, and they also serve as valuable educational tools. The authors describe the package and its implementation.","PeriodicalId":435675,"journal":{"name":"IEEE Computer Applications in Power","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133144295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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