Public Power - June 2008 - (Page 62)

Coming of Age: Superconducting Cables in a challenging state. Spurred by a number of intersecting factors, U.S. grid investment has started growing again at a substantial pace. The Edison Electric Institute estimates infrastructure spending rose to $7.9 billion in 2007—a 14 percent increase over the prior year, with much of that work devoted to meeting the nation’s burgeoning demand for power. At the same time, grid operators face reliability issues as they hit capacity limitations in both overhead T&D lines as well as underground cables. Sending too much power through a line or cable heats it to its “thermal limit” and can threaten a fault or—in extreme circumstances—produce a complete failure. In many cases, the only solution has been to attempt an upgrade of existing T&D assets. Typically that means adding more lines and cables to the system, or increasing the voltage class of lines already in place. However, almost uniform public opposition to the installation of new or higher voltage overhead lines produces an exceedingly time-consuming and expensive permitting process. From aesthetic to environmental and health concerns, overhead projects sometimes take five to 10 years to get approved. Marketplace realities such as these, and catastrophic events like the 2003 blackout, which left 50 million people without electric power showcased the imperative to modernize the grid and enhance its security. Over the past 10 years, an array of industry players, including American Superconductor Corp., have been working with HTS-based energy technologies to address these challenges. High temperature superconductors are to electricity what optical fiber has been to the communications industry: a game-changer fundamentally altering how data streams (or in the power grid’s case, electrons) are transmitted. High temperature superconductors are “smart materials” that carry vast amounts of current. In today’s congested, overtaxed power networks, some of their important characteristics include the ability to: Increase power transmission capabilities in existing rights-of-way: With a small physical footprint, HTS cables are easier to site, even in dense, older urban areas where conventional cables or overhead 62 JUNE 2008 lines are difficult or impossible to install. Their high ampacity allows them to carry substantially more AC power than conventional cables, delivered at equivalent voltage, or equivalent power delivered at significantly reduced voltage. Minimize permitting requirements: A direct benefit of increasing capacity while using existing rights-of-way is the elimination of time-consuming permitting processes. Address communities’ environmental concerns: Underground HTS cables can be installed in a narrow trench using low impact methods, eliminating the traffic congestion and run-off concerns normally associated with installation of copper-based cables. And, in contrast to conventional cables, HTS cables contain no oil. The containment and leakage issues around conventional oil-cooled cables are completely absent in this case. Nullify EMF concerns: The shielded construction of cold dielectric HTS cables means they don’t generate external electromagnetic fields (EMF), eliminating this factor as a potential objection by project abutters. Enable greater control over power flow within the grid: The significantly lower impedance of HTS power cables over conventional cables means they can relieve congestion by being placed strategically to draw flow away from overtaxed network elements. Their low impedance also enhances reliability by giving network managers greater ability to control power flows when combined with conventional products (such as series reactors or phase angle regulators) that would normally necessitate separate FACTS devices. Reduce installation and operating costs: Thermally independent of their environment, HTS cables eliminate spacing requirements and thermal backfills. Since they can operate at lower voltages, HTS cables also can avoid transformation losses and the need for expensive high-voltage equipment. Power flow problems can be managed via shorter circuit lengths—that is, connecting to more pervasive 115/138/161-kV segments rather than tying back to the more distant EHV backbone transmission system. Fault current management to increase grid reliability and security: HTS cables can adjust rapidly and automatically to power network disruptions and faults caused by weather, willful destruction or other factors. American Superconductor Corp.’s Secure Super Grids™ technology acts as a switch—instantly turning from a high-capacity conductor to a resistor when it senses too much current. Secure Super Grids systems improve the fault tolerance of entire power networks, making them self-protecting while resolving grid bottlenecks. This technology also allows for the connection of new generation resources while limiting their fault contribution. Capitalize on approaching economic parity: Steadily increasing costs of copper for transmission lines and progressively decreasing costs associated with manufacturing HTS wires affirm HTS cables as financially viable alternatives to traditional copper in many urban and metropolitan settings. The real-time need for new solutions to meet the continued demand growth and urgent requirement for T&D upgrades has triggered efforts in multiple markets to capture some or all of these important benefits. Two HTS cable systems were energized in the United States in 2006. The first, a 34.5kV cable in Albany, N.Y., links two National Grid substations. Japan-based Sumitomo Electric Industries is the HTS wire and cable supplier for this program. Another distribution-level cable was energized soon thereafter near Columbus, Ohio, on the American Electric Power grid. The project was the first demonstration of a new cable design, Southwire’s patented tri-axial HTS cable, which dramatically reduces the cost of superconductor systems and brings the technology much closer to commercial viability. A third HTS cable system was energized in late April on the grid operated by the Long Island Power Authority grid in New York. The LIPA HTS cable is the longest of the three, nearly a half mile in length. It is also the first to operate at transmission voltages. The U.S. Department of energy contributed $27.5 million of the $58.5 million project cost through its RD&D program aimed at modernizing the nation’s PUBLIC POWER

Table of Contents Feed for the Digital Edition of Public Power - June 2008

Public Power - June 2008 Contents Perspective 10 Questions Finding Common Ground on Climate Change Solutions A Patchwork Approach to Renewable Energy Whose Grid Is It Anyway? The Little Utility That Could Benchmarking Customer Service Can Prairie Hay Power Your Town? Storming the Control Room Investing in the Smart Grid Coming of Age: Superconducting Cables Community Broadband Economic Development Customer Service Human Resources For Governing Boards Safety Parting Shot

Public Power - June 2008

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