THE ELECTRIC POWER SYSTEM IS ON THE VERGE of significant transformation. For the past five years or so, work has been under way to conceptualize the shape of a 21st-century grid that exploits the huge progress that has been made in digital technology and advanced materials. The National Energy Technology Laboratory (NETL) has identified five foundational key technology areas (KTAs), as shown in Figure 1. Foremost among these KTAs will be integrated communications. The communications requirements for transmission enhancement are clear. Broadband, secure, low-latency channels connecting transmission stations to each other and to control centers will enable advances in each of the other KTAs.
· Sensing and measurements will include phasor measurement data streaming over high-speed channels.
· Advanced components, such as all forms of flexible ac transmission system (FACTS) devices, HVDC, and new storage technologies will respond to control signals sent to address perturbations occurring in milliseconds.
· Advanced control ( and protection) methods will include differential line relaying, adaptive settings, and various system integrity protection schemes that rely on low-latency communications.
· Improved interfaces and decision support will utilize instantaneous measurements from phasor measurement units (PMUs) and other sources to drive fast simulations and advanced visualization tools that can help system operators assess dynamic challenges to system stability.
Each of these elements will be applied to the modernization of the grid, at both the distribution level and the transmission level. Because it is clearly less advanced, distribution is receiving most of the initial focus. This is dramatically illustrated by the American Recovery and Reinvestment Act’s Smart Grid Investment Grants (SGIGs), announced in October.
Of the $3.4 billion awarded to 100 proposers (of the more than 400 that applied), only $148 million went to transmission applications; most of the rest was for distribution projects. While the changes to distribution will be revolutionary, transmission will change in an evolutionary manner. Distributed generation and storage, demand response, advanced metering infrastructure (SGIGs will fund the deployment of 18 million smart meters), distribution automation, two-way power flow, and differentiated power quality together represent a sea change in distribution design that will require enormous financial and intellectual capital. The role of transmission will not be diminished, however, by this new distribution paradigm. Large central power plants will continue to serve as our bulk power source, and many new ones will be fueled by renewable resources that would today be out of reach of the transmission grid. New lines will be built to connect these new plants, and new methods will be employed to accommodate their very different performance characteristics. Addressing the resulting greater variability of supply will be the job of the five KTAs listed above. As KTA technology speeds increase, control of transmission will advance from quasi-steady state to dynamic.
The traditional communications technologies capable of supporting these strict requirements are fiber optics (e.g., optical ground wire) and microwave. Recently a third candidate has appeared on the scene. Research funded by the U.S. Department of Energy (DOE) and American Electrical Power in conjunction with a small Massachusetts smart-grid communications company, Amperion, has demonstrated the viability of broadband over power line (BPL) for application on transmission lines. Currently, a five-mile, 69-kV line is operating at megabit-per-second data rates with latency of less than 10 ms. The next step will be to extend this high voltage BPL technology to 138 kV.
Authors: S.H. Horowitz , A.G. Phadke and B.A. Renz
Source: IEEE Power & Energy Magazine
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