ORNL researchers evaluate ways to make the U.S. electric system more reliable and less likely to experience a large blackout.
On August 14, 2003, during the largest electricity blackout in U.S. history, "communications were disrupted, traffic was snarled, elevators stopped, air conditioners quit, stores and businesses were forced to close, factories shut down, and hospitals and other vital facilities went to emergency power," according to a Department of Energy report.
"This blackout was largely preventable," said Secretary of Energy Spencer Abraham in his November 19 remarks announcing the U.S.-Canadian Power System Outage Task Force's Interim Report on causes of the blackout. The report, he added, ".showed that once the problem grew to a certain magnitude, nothing could have been done to prevent it from cascading out of control."
Two ORNL researchers—Brendan Kirby and John Kueck, both in the Engineering Science and Technology Division (ESTD)— served on the task force's Electric System Working Group. Kirby, an international expert on improving power-grid reliability and using electrical loads as a resource, said that he and Kueck interviewed employees of electric power systems in the Northeast and Midwest. They also analyzed tapes of telephone calls between operators at the control centers of the affected power systems.
"We found that the failure of power system operators to notice that an alarm system had stopped functioning and lack of human communication contributed to the blackout," Kirby says. "Multiple transmission lines failed, and the people who needed to know about these failures didn't find out until it was too late."
Researchers in ORNL's Office of Electric Transmission and Distribution Technologies Program have been evaluating new ways to reduce congestion on the nation's electric system infrastructure, improve its reliability, and prevent future blackouts. On hot days when air conditioning is in high demand, today's electric power lines can suddenly be forced to carry high current at temperatures higher than their normal operating level. Because of the properties of these steel-core-aluminum conductor cables, these overloaded lines can sag into trees, causing short circuits. Line overload and sagging became a problem in the August 14 blackout.
"Utilities may be willing to replace their conventional power lines with advanced conductors if they see proof the conductors have significant advantages," says program manager Bob Hawsey. "We can show them proof that advanced conductors carry more current without the same degree of sagging at the National Transmission Technology Research Center (NTTRC), operated by ORNL in partnership with the Tennessee Valley Authority."
At NTTRC's Powerline Conductor Accelerated Testing facility at ORNL, John Stovall and Tom Rizy, both of ESTD, have been subjecting advanced conductors to thermal, electrical, mechanical, and environmental "stress" tests while simulating 20 to 30 years of power transmission in several months of testing. They showed that 3M's composite-core conductor, which consists of ceramic fibers inside an aluminum-zirconium matrix, can carry 2.5 to 3 times the current of heavier conventional steel-core lines at 2.5 times the operating temperature before sagging the same amount.
Other technologies evaluated at ORNL that might have prevented the blackout are real-time communication and control technologies, including power electronics to control reactive power. These technologies could have made the operators of the affected systems aware of the location and impact of transmis-sion-line failures and helped them respond quickly to prevent spread of the voltage collapse.
To improve electric reliability, Kirby advocates the concept of "spinning reserve" from responsive load instead of having generators standing by ready to provide reserve power. Several trial demonstrations of this concept are being developed in various parts of the nation by ORNL. One example is a rapid and temporary reduction of hotel and motel room air-conditioning loads when a problem develops within the power system. Demonstrations show that utilities can page a hotel's supervisory controls to turn off room heating or cooling systems for 10 to 30 minutes to drop the hospitality industry's demand for power by one-third without affecting occupants' comfort. These ORNL technologies, if widely deployed, could help the nation avoid grid grief.
Web site provided by Oak Ridge National Laboratory's Communications and External Relations