WASHINGTON -- Federal regulators two years ago identified at least 15 choke points in the power grid between New England and California, places where congestion can quickly overwhelm electricity transmission lines and cause blackouts.
An analysis by the Federal Energy Regulatory Commission in 2001 found one of the worst problems in the line moving power from upstate New York into metropolitan New York City -- areas hard hit by Thursday's blackout.
Traffic on the line was particularly severe several summers ago. Outages at a nuclear power plant north of New York City had forced greater reliance on substitute power from upstate and put more stress on the transmission system, the analysis said.
A second choke point was the grid in Central and Southern California.
A national grid study by the Energy Department last year found 50 of 186 transmission paths in the East were used to their maximum capacity at some point in the year, with 21 congested at least 10 percent of the time.
The department said its analysis "confirmed the tendency for transmission lines to become congested in many locations across the U.S."
Of those, a line in western Pennsylvania and one connecting Pennsylvania with western New York were the most congested, 80 percent or more of the time. Lines between Minnesota and Wisconsin, South Dakota and Missouri, Alabama and Florida, and Georgia and Florida were congested 60 percent to 79 percent of the time.
In the West, 37 of 106 transmission paths were found congested at some during the year, but none more than 60 percent of the time. Those between Montana and southwestern Wyoming and between northern Idaho and northwestern Washington state were congested at least half the time.
Congested between 40 percent and 49 percent of the time was a transmission path connecting southwestern Wyoming with Utah, Nevada and Southern California.
In last week's blackout, investigators were focusing on the massive grid encircling Lake Erie that moves power from New York to Detroit, into Canada and back to New York.
The New York and California bottlenecks are in states that moved aggressively to deregulate their energy markets, leading faraway suppliers to compete for limited space on transmission grids.
The FERC said the cost to consumers nationally from not adding more capacity to alleviate those choke points was more than $1 billion in added electricity costs over the summer, though the improvements could pay for themselves in energy savings.
Other choke points were found in a grid connection between Wyoming and Idaho, southeastern Pennsylvania, a line northeast of Boston and a line carrying power from West Virginia into the mid-Atlantic power market area.
Transmission lines in the United States are divided into three regional grids: the East, which extends from the Atlantic Coast to the Rocky Mountains; the West, which covers the Rocky Mountain region to the Pacific Coast; and Texas, which has its own grid.
Lawmakers such as Sen. Larry Craig, R-Idaho, noted Friday that industry experts have been predicting the power grid failures.
"While deeply troubling, it is not especially surprising to me that there has been a failure of a major North American power grid," said Rep. Billy Tauzin, R-La., chairman of the House Energy and Commerce Committee.
He said his committee was beginning an investigation into the blackouts and promised a hearing in early September.
Connect with the Southeast Missourian Newsroom:
For corrections to this story or other insights for the editor, click here. To submit a letter to the editor, click here. To learn about the Southeast Missourian’s AI Policy, click here.