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Stressed-out grid jeopardizes U.S. power supply

Why can’t America’s system of high-voltage transmission lines get power to where it’s needed? A look at the overstressed grid and why it isn’t being upgraded quickly enough.
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As the summer draws to a close, Americans are looking back and asking: What happened to all those dire predictions about power shortages? Cost-conscious consumers and cooler-than-normal weather in states such as California helped the nation escape an energy meltdown. But the bullet America dodged this summer doesn’t change a grim reality: The nation’s power delivery system is fragile and outdated.

The nation has plenty of generating capacity, but its antiquated power grid can’t always deliver. Worse, prospects for expanding and improving the grid don’t look good, because of the high cost of building new transmission lines and a thicket of government regulations.

First, a look at the overtaxed grid by University of Illinois Professor Thomas Overbye, who offers the perspective of an engineer who has done extensive studies on the grid’s reliability.

“Interstate shipment of electric power takes place all the time, but there is just not enough transmission capacity to meet all of the needs,” he said. That’s because “the high-voltage electric transmission system was originally designed to meet the needs of local utilities,” Overbye said, not for shipping electric power over hundreds of miles.

Whether in California or New York, the demand for electric power runs up against something even more implacable than government regulation — the laws of physics.

“If you run too much electricity through an extension cord, it heats up,” Overbye explained. “Likewise on a high voltage line. As you put more electric power down a wire, the line starts to heat up. Just like any metal, it expands and when a transmission line expands, it starts to sag. If it sags too much, eventually it’s going to hit something beneath it.”

In the summer of 1996, for example, power being shipped over a high-voltage line in Idaho arced over to a tree, causing a blackout that shut off power to 2 million people in 14 Western states.

The danger of sagging lines is exacerbated in the summer when the cables are heated both by the current flowing through them and the air temperature around them.

“You can’t put as much power through a line when it is 95 degrees out and the sun is beating down on it” as you can when the weather is cool, Overbye said

The risk of grid failure skyrockets when temperatures differ widely between one region of the country and another.

Why? Because those are the times when the most power has to be shipped across great distances.

Last year, “heavy north-to-south power transfers occurred throughout the summer, spurred by cooler-than-normal temperatures in the North and extremely high temperatures in the South,” according to the North American Electric Reliability Council, the non-profit agency that sets the operating standards for the nation’s regional grids.

As a result, the council says, there were plenty of times when the north-to-south transmission interface in the Tennessee Valley Authority was loaded well beyond capacity.

The nation’s grid is riddled with vulnerable stretches of power lines, analogous to the weak wall of a human artery that could be blown out by an aneurysm.

A notorious weak link is California’s Path 15, which runs from Coalinga to Los Banos in the state’s Central Valley. In normal summers, northern California utilities can buy power from the Pacific Northwest, but for the past two years Oregon, Washington and Idaho have had such poor hydroelectric generating conditions that northern California has had to turn to southern California and Arizona to buy power.

The problem is that the grid was not built to ship power from southern California to northern California, said Dennis Eyre, executive director of the Western Systems Coordinating Council, the agency that polices the grid in the western United States.

“No one ever assumed that all these conditions would come together at the same time,” Eyre said.

Why don’t the utilities build more high-voltage lines to bring electricity into power-starved states?

Utilities say that just to maintain current transmission capability would require $56 billion in new investment during the present decade. They argue that state regulations deter them from making the necessary investments.

Historically, transmission has been regulated by state public utility commissions and by the federal government.

“There’s a real question whether the returns on investment are adequate to convince people to make the investment” in building new power lines, said David Cook, general counsel of the North American Electric Reliability Council. “The traditional rate treatment would amortize the cost of a transmission investment over 30 years at a modest rate of return. In this day and age people can invest their money in other places” more quickly and more profitably.

Another barrier to building more transmission lines is the daunting array of local and state agencies that need to OK the siting of a line. “This patchwork of local siting authority has effectively thwarted the building of transmission facilities necessary for interstate commerce,” said William Massey, a member of the Federal Energy Regulatory Commission.

Massey, a Democrat appointed to the commission by President Clinton, supports President Bush’s call for legislation that would give the federal government the power to obtain rights-of-way for electricity transmission lines — similar to the authority the federal government already has for siting natural gas pipelines.

But the nation’s governors oppose any federal takeover of transmission line siting decisions. And it appears doubtful that Congress will give the federal government right-of-way powers any time soon.

In addition, “not-in-my-backyard” resistance and complex land use questions make it extremely difficult to build new lines.

Take a case in southwestern Virginia: No new transmission lines have been built in the region since 1973, even though demand for power has increased by 136 percent.

American Electric Power has been trying for 10 years to built a 765-kilovolt transmission through the southwestern part of the state, but environmental groups and the U.S. Forest Service blocked one proposed route because it would have crossed the Appalachian Trail and other scenic places.

Finally, last May, Virginia regulators gave the utility the go-ahead.

So electricity users, take a memo for next summer: It’s not easy to build new transmission lines to bring you the power you want, and it isn’t going to get any easier in the years ahead.