◆ Communication Network Architecture and Design Principles for Smart Grids Kenneth C. Budka, Jayant G. Deshpande, Tewfik L. Doumi, Mark Madden, and Tim Mew An integrated high performance, highly reliable, scalable, and secure communications network is critical for the successful deployment and operation of next-generation electricity generation, transmission, and distribution systems—known as “smart grids.” Much of the work done to date to define a smart grid communications architecture has focused on high-level service requirements with little attention to implementation challenges. This paper investigates in detail a smart grid communication network architecture that supports today’s grid applications (such as supervisory control and data acquisition [SCADA], mobile workforce communication, and other voice and data communication) and new applications necessitated by the introduction of smart metering and home area networking, support of demand response applications, and incorporation of renewable energy sources in the grid. We present design principles for satisfying the diverse quality of service (QoS) and reliability requirements of smart grids. © 2010 Alcatel-Lucent. Introduction The global electric power industry is entering a cells is being deployed in homes and enterprises. period of significant transformation. Generation, Introduction of alternate and renewable sources of transmission, distribution, and control infrastructure energy and new storage technologies is fundamen- are aging while energy consumption is increasing. tally altering the centralized power generation and Figure 1, which was developed using data from the distribution paradigm that predominates today. U.S. Department of Energy [18], illustrates the trend Furthermore, variations in the output power of renewa- in worldwide electricity consumption between 1980 ble sources caused by changes in weather and time and 2006. of day are driving the control of distribution networks Smart metering and other demand-side tech- to finer and finer time scales. niques have become increasingly necessary to control “Smart grid is a concept for transforming . [the] demand during peak and off-peak hours. Industrial- electric power grid by using advanced communica- scale wind and solar power plants are being connected tions, automated controls, and other forms of infor- to the grid as part of worldwide efforts to reduce car- mation technology. This concept, or vision, integrates bon emissions. Smaller-scale micro-generation in the energy infrastructure, processes, devices, information, form of small wind turbines and photovoltaic (PV) and markets into a coordinated and collaborative Bell Labs Technical Journal 15(2), 205–228 (2010) © 2010 Alcatel-Lucent. Published by Wiley Periodicals, Inc. Published online in Wiley Online Library (wileyonlinelibrary.com) • DOI: 10.1002/bltj.20450 Panel 1. Abbreviations, Acronyms, and Terms AC—Alternating current NASPInet—NASPI network ADR—Automated demand response NERC—North America Electric Reliability AMI—Advanced metering infrastructure Corporation BPL—Broadband over power line NIST—National Institute of Standards and CCTV—Closed circuit television Technology CDMA—Code division multiple access OFDM—Orthogonal frequency division CPP—Critical peak pricing multiplexing CS—Class selector OSI—Open System Interconnection DER—Distributed energy resource P2P—Peer-to-peer DiffServ—Differential services PEV—Plug-in electric vehicle DSCP—Differential services code point PHEV—Plug-in hybrid electric vehicle DSL—Digital subscriber line PLC—Power line carrier EDGE—Enhanced data rates for GSM Evolution PMU—Phasor measurement unit EF—Expedited forwarding PRIME—PoweRline Intelligent Metering EMS—Energy management system Evolution EPRI—Electric Power Research Institute PTT—Push-to-talk GPON—Gigabit passive optical network PV—Photovoltaic (cells) GPS—Global positioning system QoS—Quality of service GSM—Global System for Mobile RF—Radio frequency Communications RFC—Request for comments GtCO2e—Giga (metric) tonne carbon dioxide RTO—Regional transmission organization equivalent RTP—Real time pricing HAN—Home area network RTU—Remote terminal unit HSPA—High-speed packet access SCADA—Supervisory control and data IEC—International Electrotechnical Commission acquisition IED—Intelligent electronic device SDH—Synchronous digital hierarchy IEEE—Institute of Electrical and Electronics SONET—Synchronous optical network Engineers TDM—Time division multiplexing IETF—Internet Engineering Task Force TOU—Time of use (pricing) IntServ—Integrated services UMTS—Universal Mobile Telecommunications IP—Internet Protocol System ISM—Industrial, scientific, and medicine UPS—Uninterruptible power supply ISO—Independent system operator VAR—Volt-ampere reactive L1, L2, L3—Layer 1, 2, 3 (of OSI model) VoIP—Voice over IP LAN—Local area network VPN—Virtual private network LMR—Land mobile radio VVWC—Volt, VAR, Watt control LTE—Long Term Evolution WAMS—Wide area measurement system MDMS—Meter data management system WAN—Wide area network MPLS—Multiprotocol Label Switching WiMAX—Worldwide Interoperability for NAN—Neighborhood area network Microwave Access NASPI—North American SyncroPhasor Initiative process which allows electricity to be generated, dis- This paper addresses network architecture and tributed, and consumed more effectively and effi- design principles for an integrated smart grid commu- ciently” [13]. A high performance, reliable, and secure nication network. We examine some of the challenges communication network is one of the fundamental faced in supporting a diverse set of applications each building blocks to the introduction of smart grid appli- with varying network performance requirements, relia- cations. bility requirements, and traffic characteristics, as well 206 Bell Labs Technical Journal DOI: 10.1002/bltj 18,000 Asia & Oceania 16,000 Africa Middle East Eurasia 14,000 Europe Central & South America 12,000 North America 10,000 8,000 6,000 Energy consumption in billion KWH 4,000 2,000 0 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 P2006 Year Electricity demand is increasing in Asian countries, and in China in particular, which saw demand for energy grow nearly tenfold over a 25 year span. The North American market experienced a twofold increase over the same period despite drastic reduction in the manufacturing industry and slow population growth. Along with the pent up demand, energy sources are becoming scarce and the cost of generating electricity is becoming prohibitive. Therefore, making efficient use of electric energy should, in theory, help reduce dependence on fossil fuel and combat carbon emissions. Figure 1. Worldwide electricity consumption. as the challenges faced with supporting legacy appli- applications including brief descriptions of the appli- cations and networks. While there are many legacy, cation examples listed above. A smart grid communi- new, and evolving applications, the following five cation network architecture is presented including the classes of applications (not necessarily mutually exclu- physical connectivity architecture, examples of logical sive) will be used as examples in presentation of connections, access network options, and the archi- communication network architecture and design prin- tectural implications of shared ownership of networks. ciples in this paper: We then address specific quality of service (QoS) and • Smart metering, also known as advanced meter- reliability design considerations for integrated smart ing infrastructure (AMI), grid communication networks. We illustrate the • Automated demand response (ADR), “green benefits” of a smart grid—and by implication • Teleprotection, those of the integrated communication network—and • Distribution automation, and offer our conclusions and recommendations on areas • Micro grid management. for future work. We begin with an overview of the evolution of a Complete treatment of smart grids requires dis- traditional power grid to the smart grid. Next, we cussion of a wide variety of technologies and topics. present a high-level characterization of smart grid Due to space restrictions, we have had to limit scope. DOI: 10.1002/bltj Bell Labs Technical Journal 207 An essential topic not addressed in this paper is net- from consensus-gathering workshops attended by work security—a topic worthy of several papers on representatives from government agencies, regula- its own. Furthermore, details of local area networks tors, vendors, (communication) service providers, (LAN) or home area networks (HAN) are outside of academia, and standards organizations. Some of the the scope of this paper. earlier EPRI work on IntelliGrid* can be found in [6]. The following brief smart grid presentation will An Overview of Smart Grid be used to set context for network architecture and There is a wealth of information on the smart grid design. In a traditional power grid of an electric power concept and its evolution in the public domain. The system (or utility), electricity flows from bulk power most comprehensive smart grid overviews are found generators to consumers over a grid of transmission in the 2009 reports to U.S. National Institute of lines and distribution feeders, as shown in Figure 2. Standards and Technology (NIST) prepared by the A hierarchy of transmission lines is connected Electric Power Research Institute (EPRI) [5] as well as through a series of transmission substations leading the final NIST Framework and Roadmap document to distribution substations at the edge