Distribution management systems
The theme for this issue is distribution management systems (DMSs). The power distribution system is a critical element of the developing smart grid as it is the interface between widespread distributed resources (distributed generation, distributed renewable resources, distributed storage, demand response, active customer loads, electric vehicle charging and discharging) and the entire power grid. These resources must be integrated while maintaining (and even improving) reliability levels and also optimizing the management of both legacy and new distribution infrastructure, without compromising safety and protection of distribution assets. The DMS can be viewed as a logical extension to state-of-the-art systems in use today (fault location, automated reconfiguration, and voltage and volt-ampere reactive (var) control). However, the most important value of the DMS is, arguably, the ability to combine these functions for more integrated management and optimization. We believe that the DMS will be one of the most critical elements of the smart grid and we commend the editorial board for selecting this topic for an in-depth examination.
The first generation of the DMSs started appearing in the 1980s and were intended for improving the performance of legacy distribution systems that were characterized by the lack of flexibility and intelligence, aging infrastructure and controls, low reliability and efficiency, increased consumer cost of service issues, and environmental issues. Legacy systems generally implement specific functions as individual applications. Supervisory control and data acquisition applications provided monitoring and control down to distribution feeder breakers and, in a few cases, beyond the feeder circuit breaker out on the feeders themselves (outside the substation fence). Voltage and var control are implemented at individual (standalone) capacitor banks and regulators. Since these early systems lacked communication networks, coordination between devices was handled via time-coordinated controller settings based on planning studies. Demand response systems were typically implemented based on central controls with little coordination at the distribution level.
In recent years, automation systems for reliability improvement have developed in a variety of ways. Intelligent schemes for system reconfiguration have been applied with and without coordinated communications and central control. In addition, advanced fault location applications have reduced fault investigation time, resulting in faster restoration times.
The second generation of the DMS started appearing in the last decade. The important concept for these next generation systems is the integration of functions. Coordination of DMS applications can improve the performance of the distribution system and operator effectiveness. The article “I Sing the Mapboard Electric” in this issue describes this concept quite effectively.
The impetus for the third or current generation of the DMS came from the unprecedented technological and institutional changes that started happening since the dawn of the 21st century, resulting in the smart grid concept. The U.S. National Energy Technology Laboratory identified five foundational key technology areas to meet the new challenges and opportunities of the smart distribution grid:
sensing and measurements
advanced control schemes
improved interfaces and decision support systems.
Advanced automation needed for future smart distribution systems requires faster and more accurate decisions and thus real-time analysis of distribution systems. A robust and dynamic simulation engine and system model is at the heart of the next generation system management. This simulation engine and model will allow integration of smart customer interfaces, distributed resources, and new types of loads (electric vehicles) with all of the DMS functions that have already become standard. The input data for analysis includes system topology, parameters of different components in the system, status of switches and breakers, and measured data from various points in the system (including advanced metering data from virtually every customer). As more data is measured, the analysis becomes more complex. The analytical tools should be able to use this data effectively. Real-time analysis will allow faster control of distribution systems. For example, the system can be reconfigured frequently in response to load and other system changes by opening and closing switches to bring it to a new optimal state. Such operation would require more robust switches that can handle multiple opening and closing operations without failing. Solid-state switches would be the answer for some of these applications.
Real-time monitoring and analysis can also lead to faster and more effective system restoration following emergencies. System reconfiguration can take advantage of load control, demand response, and distributed resources to restore sections that previously could not be transferred due to load constraints. These new approaches can include stepped restoration to account for special load characteristics such as inrush. Advanced concepts like microgrids can further improve reliability for special requirements.
These next-generation DMS applications require new communication system infrastructures (including technologies for cybersecurity requirements), monitoring and control technologies, and integration of systems. Interoperability standards to help achieve this integration will be particularly important. We think that the articles in this issue will help provide the reader with an excellent overview of the technologies and approaches for the next-generation DMS.
In This Issue
The seven articles compiled for this issue provide an excellent overview of plans and technologies for smart distribution systems in general and distribution management systems in particular. The reader will get an overview of the variety of different approaches that are being taken to develop the next generation distribution system. Although there are many different approaches being taken, the common themes of maintaining reliability, optimizing asset management, and integrating the wide variety of distributed resources and advanced customer systems are evident throughout all the contributions.
The first three articles deal with the “tale of three utilities” on their vision and developments to date on their respective smart distribution grid operations. The first article, “Good Vibrations” is by Robert J. Yinger and Ardalan E. Kamiab, two veterans in this field. The article starts with a brief description of California's timeline for smart grid development and the important drivers that are behind this timeline. This California perspective provides the frame of reference for the Southern California Edison specific timeline and goals for implementing the smart grid and smart distribution system. The Distribution Circuit of the Future project was recently completed and provides the technology foundation for next step implementations. The article then presents the next steps in applying advanced technologies as part of the overall system management. This is referred to as the system of the future, and the demonstration is being conducted in Irvine, California, where four distribution substations are interconnected with a looped topology. This approach truly reflects the fundamental change that will reflect the future of improving system reliability. This is an ambitious undertaking but has the support of the U.S. Department of Energy. The authors conclude the article by stressing the importance of new technologies integration with the existing system for optimizing the system performance and the need for proper planning.
The second article, “I Sing the Mapboard Electric” by Larry Clark and Ethan Boardman, describes the evolution, justification, and development of next generation distribution management at Alabama Power. The key to this next generation distribution management is technology integration so that the operator is able to access information from all elements of distribution management with convenient displays and interfaces. Though not covered in this article explicitly, Alabama Power's approach for advancing automation stems from the deployment of “smarts,” such as smart switches, smart reclosers, smart capacitors, and smart sensors in their feeder system to realize effective feeder automation. This is indeed a very practical approach they have been systematically undertaking in the last 20 years or so.
“Power Steering” by Sébastien Grenard, Olivier Devaux, Olivier Carré, and Olivier Huet describes the deployment of many advanced distribution automation functions undertaken at Electricité de France (EDF). The article describes the characteristics of advanced distribution automation (ADA) at EDF and the different architectures that can be used to implement advanced automation functions, from completely centralized management to distributed control with intelligence in individual devices. Different solutions may be appropriate for different systems but most are likely to employ a combination of central and distributed control. The article describes the result of research into optimizing the monitoring and switch placement requirements to achieve reliability and system optimization objectives. Their philosophy is reflected in the closing statement of the article.
The first three articles attributed success to the availability of new technologies for the latest generation of DMS development. The fourth article by Clark Gellings provides a thorough and comprehensive treatment of new technologies on the horizon. This is a very important resource that readers should take note of. Some of the evolving technologies covered include intelligent reclosers and relays, power electronics devices including distribution short circuit current limiters, advanced sensors, intelligent universal transformers, solid-state switchgear, fault anticipators, advanced metering infrastructure (AMI), and, finally, distributed energy resources and energy storage facilities that are equipped with smart inverters. Gellings makes a convincing case for new technologies.
The fifth article by Sumit Roy, Dan Nordell, and S.S. (Mani) Venkata provides the communication perspective for smart distribution grid operations. They provide their vision and justification for the development of smart distribution grid infrastructure integrated with a proper communication infrastructure at different distinct layers from distribution substation to customer management systems. They also provide a treatment of communication network standards for smart grids. This is then followed by a detailed treatment of the characteristics of smart communication infrastructure at different layers. The ubiquitous issue of cyber security is also addressed in this article.
The sixth article, “Sim City” by Roger Dugan and Mark McGranaghan starts with the characteristics of an active distribution system. This is followed by the integration requirements for evolving distribution system models. They also make a convincing case for the need of accurate load models, a distribution planning function, for effective DMS development in the section “Modeling the Distribution Control Architecture and Systems.” This article concludes with a convincing case for proper industry coordination. They then describe the development of the IEEE 8,500-node system model that can be used to benchmark next generation distribution simulation tools.
Finally, the article “Tools for Success” by Julio Romero Agüero provides a thorough and comprehensive treatment on this subject. Today's power distribution planning engineers require new software tools and analytical methods to ensure that future distribution systems can accommodate the influx of distributed energy resources without adverse effects and also exploit the opportunities provided by these devices. Smart operations require smart planning. We agree with Romero that the implementation of the smart distribution concept and the deployment of smart grid technologies on power distribution systems are leading to the emergence of a number of challenges to the way distribution systems are planned and operated. Furthermore, this trend is also providing planners with abundant data at the feeder, distribution transformer, and customer levels. To address these challenges, new methodologies and computational tools are needed that make efficient use of the available data and allow for integrated resource planning and multiobjective optimization. The article makes a convincing case for conducting these studies via commercially available distribution analysis software and also cautions that specialized skills are needed for conducting the complex and time-consuming planning process. This is an area where further improvement and work by software developers is required and where collaboration between industry members is crucial. Finally, we agree that smart grid planning is radically different from legacy system planning.
The seven articles cover a wide spectrum of issues related to the development of advanced distribution management systems. We hope these articles help put this broad topic in perspective for IEEE Power & Energy Magazine readers and provide a foundation for more detailed investigations. We also hope this issue will be useful source of reference for those who are currently undertaking, or will undertake, the development of future DMS systems. For further insight into any of the topics covered in this issue, you are encouraged to go through the recent literature and the “For Further Reading” references cited at the end of the articles. We also strongly encourage the readers to read the “In My View” column by Anil Pahwa at the end of this issue. In this column, Pahwa covers the chronological developments of DA to ADA and different generations of DMSs very logically and systematically.