Ed Gray, NEMA
To maintain reliability and provide consumers with the benefits of competitively priced electricity, additional investments are required to expand transmission capacity and eliminate bottlenecks. This capacity can be developed by expanding existing facilities, maximizing the capacities of existing transmission equipment through use of information technology and controls, and/or the development of new facilities.
The Department of Energy National Transmission Grid Study (NTGS-May 2002) generally identifies transmission bottlenecks and calls for a study of existing transmission rights of way with the capability for additional capacity.
Technology offers solutions
Technologies, such as those discussed below, are available today that can significantly enhance the power flow capacity of the existing transmission system. These can be used on existing transmission line rights of way with minimal impact to the public. Better insulators allow increasing the voltage on transmission lines (e.g., to 765 kV) and the addition of multiple conductors per phase can significantly increase the capacity of existing lines. New advanced conductors, such as aluminum conductor steel supported trapezoidal wire (ACSS/TW) technologies, can increase power carrying capacity by 30-100 percent. The use of high voltage direct current (DC) transmission, already in place in some areas of the Northwest, Southwest and Northeast, can nearly double transmission capacity and improve system stability.
Technologies also can make a significant contribution in improving the efficiency of electricity transmission and distribution. About 10 percent of the electricity generated is lost during the transmission and distribution process. The use of more efficient transformers can increase efficiency by about 5 percent. Power factors (the fraction of electric current that can do useful work) can be improved through the use of capacitors or synchronous condensers, as has been done in the San Francisco area.
Other technological options that can introduce greater intelligence into the transmission grid are available. FACTS (Flexible AC Transmission Systems) technology and wide area controls have been used to increase power flow capability on stability-limited lines by as much as 40 percent. The installation of real-time metering on transmission lines permits the determination of actual currents, which can be used to calculate limits, rather than conservatively assumed electrical currents. The use of real-time dynamic rating technologies to assess the capacity of transmission systems based on actual weather conditions and line currents can increase the power carrying capability of thermally limited lines by up to 15 percent. Software tools are available that can more accurately calculate stability and thermal limits on transmission lines in real time, producing an increase in power transfer capability of as much as 10 percent.
Need for new regulatory approach
These new transmission technologies are not in widespread use because under current regulatory policies and uncertainties, transmission owners have little incentive to deploy them. Investments in transmission infrastructure in recent years have lagged far behind historical investment levels and the growth in demand for electricity. With the bankruptcy of Enron, the financial community is making utility investments still more difficult.
Relative to generation, the transmission system represents a small percentage of the total cost to the electricity consumer (about 10 percent). Federal Energy Regulatory Commission (FERC) staff, in a study released in December 2001, reported that significant transmission investments would either not increase rates much, or more likely reduce them, as low cost generation would be available to more customers.
Incentive and performance-based rates should be structured to promote not only investments in new transmission lines, but also deployment of new transmission technologies like those discussed above, that will improve reliability, availability, power factors and energy efficiency. Transmission owners receive no benefit under current regulation for running transmission smarter, or more reliably. Locational Marginal Pricing (LMP) is proposed as a solution to reducing congestion, however, while it makes power delivered over congested lines cost more, it does not necessarily encourage (and may arguably disincent) the transmission owner to reduce the congestion. Reduced tax life for transmission assets would also encourage investments.
Technologies exist today to upgrade our existing patchwork transmission system into a vibrant, 21st century interstate electricity highway system. What are missing are the mechanisms to encourage this investment.
Gray, director, energy policy, at NEMA has 30 years experience in the electricity business at NEMA, the Electric Power Research Institute, and the Tennessee Valley Authority. He can be reached via e-mail email@example.com.
NEMA is a U.S. trade association representing the interests of electroindustry manufacturers. Founded in 1926 and headquartered near Washington, D.C., NEMA’s 450 member companies manufacture products used in the generation, transmission and distribution, control, and end-use of electricity.