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ECE Profs Study Technical Impact of Utility Deregulation

As part of an international shift toward free markets, America's electric utilities are moving toward limited deregulation. Changes in the way federal and state governments regulate the sales of electricity may soon allow consumers to choose between a variety of power providers--including those in distant states--the way they now select long-distance phone companies. But letting consumers buy power from remote suppliers poses a host of technical problems. Members of the Department of Electrical and Computer Engineering's Power Systems Group--including Fernando L. Alvarado, Christopher L. DeMarco, Ian Dobson, Robert H. Lasseter and Robert Long--are working on the modifications that will have to be made in the nations electrical-transmission grid to make these regulatory changes possible.

Traditionally, for any given area, a single utility generates power and distributes it primarily along power lines it owns. The utility also may exchange power with neighboring utilities on a limited number of transmission lines, but these exchanges are closely regulated. That makes managing the system relatively easy: As customers demand more power, the utility generates more and sends it into the grid. Because that utility controls its own portion of the system, it knows that the grid isn't being overloaded.

Ian  Dobson

Ian Dobson (large image)

But in most projected versions of free-market electricity sales (or "retail wheeling"), electricity producers will be free to send power along other utility's transmissions lines--which will still be under some kind of regulatory control--across state borders to any customer. Thousands of rapidly changing, long-distance transactions may flood the thousands of power grids that will increasingly act as a large, interconnected grid. "That's where it gets tricky," says Dobson, "because the electrons don't flow just between those two parties, they flow throughout the entire network according to the laws of physics." And that means both that power lines will have to carry more electricity than under the present system and that exactly which lines will carry an extra load at any instant will bedifficult to predict. "If you keep putting more and more power through a section of a transmission grid, eventually it won't take any more," he explains. "You'll get oscillations or blackouts or lines tripping or lines getting too hot."

One possible solution, DeMarco says, might be to place semiconductor switching stations at critical locations in the grid. These Flexible Alternating Current Transmission Systems (FACTS)--$40-million conglomerations of Frisbee-sized transistors and associated circuitry--are similar to the power electronics found in household light dimmers or variable-speed motors. They switch in and out of the electrical waveform at specific points, hundreds of times a second, to change the transmission line's resistance to electricity, or impedance. "If we could control those impedances, then we could encourage power to flow through one part ratherthan another part," Dobson says.

Christopher L. DeMarco

Christopher L. DeMarco (large image)

"What you're trying to achieve," DeMarco explains, "is to be able to dial how many megawatts you want to flow on this transmission line, independent of whatever else may be going on around you." Exactly what effect large numbers of these fast-acting devices might have as they interact with the transmission system and power generators, however, isn't known. FACTS can, for example, add harmonic distortion to the electrical waveform, degrading the value of power for sensitive devices such as computers. These harmonics may also affect other switching stations or even generators, causing them to malfunction. Using mathematical models and computer simulations, DeMarco and Dobson are finding ways to both predict these interactions and design against failures they potentially could cause.

With just a few circuit elements representing the power system and semiconductor switches, Dobson and Lasseter have detected the potential for effects on the power grid ranging from low voltages to catastrophic failures. "They can go unstable in ways you haven't thought of," Dobson says. Certain applications of FACTS, for example, could cause electrical current to flow in unpredictable patterns, stressing the power system. "One of our functions is to try and understand the full range of behavior of these circuits so that these events will definitely never happen," Dobson says. "Sometimes very simple solutions can keep you away from these kinds of regions of operation."

It is possible, however, that in a deregulated environment not everyone will want to keep all parts of the system working well. DeMarco is investigating the potential for mischief that these regulatory and technical changes will introduce. The very problems introduced by interactions between interconnected transmission grids, generators and devices such as FACTS could allow a negligent, or even unscrupulous, utility to gain a advantage over their competing power merchants.

Intrigued by these ideas, DeMarco ran models to see if in a deregulated operating environment, one operator could configure its generators in such a way as to create problems in a competitor's generators. "The answer turned out to be: easily, yes," DeMarco says. "It's not hard to create an oscillation that is experienced primarily by your neighbors, or someone fairly distant, provided the grid connection is there. And of course, once the generator starts oscillating to a significant degree, it is forced to disconnect from the network or risk damage."

Potential for mischief aside, the continuing growth in electrical demand means that strategies such as FACTS would soon be needed, even if utilities were to remain under current regulations, Dobson says. These systems can maximize the amount of power a network can carry. And although at a cost of in the tens of millions of dollars they're not cheap, "that's nothing compared to the cost of building new transmission lines," Dobson adds.