High-voltage power towers 'twisted like bow ties'

High-voltage power towers 'twisted like bow ties'

May 3rd, 2011 by Pam Sohn in News

Damaged transmission lines at TVA's Widows Creek Fossil Fuel Plant block Jackson County Highway 96 in Bridgeport. Staff Photo by Dan Henry - The Chattanooga Times Free Press


Story and video: Sen. Alexander tours destroyed homes in Apison

With more than 90 high-voltage power transmission lines bent like pipe cleaners by the tornadoes, about 119,000 customers in TVA's seven-state region were still without electricity Monday evening because TVA couldn't supply its distributors.

"We saw TVA power transmission lines twisted like bow ties," said Eric Holweg, a National Weather Service meteorologist.

Holweg, who was in Bradley County on Friday, called damage there the worst he's ever seen.

TVA spokeswoman Barbara Martocci said the agency has tasked more than 4,000 utility crewmen and contractors to reroute and make temporary repairs to the 500-kilovolt and 161-kilovolt lines, which carry electricity from TVA power plants to distributors such as EPB and North Alabama Electric Cooperative, which serves Bridgeport.

At peak, 675,000 TVA-supplied homes were without power because of the downed transmission lines, officials said.

"We're focusing on restoring power to critical infrastructure such as Browns Ferry Nuclear Plant and hospitals," Martocci said Monday. "But there are some of the 90 lines that can't be repaired. We know we will have to rebuild the North Alabama 500,000-volt line system."

In the meantime, the utility will "go around them," by using combinations of the 161,000-volt lines to reroute electrical grids, she said.

"The analogy given to me is that the 500,000-volt lines are like Interstate 75, and the 161,000-volt lines are like your other four-lane highways around the interstate," she said.

The Band-Aid approach, which now has restored connections to about 90 percent of the distributors, was made necessary by an unprecedented 362 tornadoes that pummeled the Southeast. The most violent and longest-tracking storms dropped on Tennessee and Alabama, weather tracking maps show.

National Weather Service tornado damage assessment teams have said an EF4 tornado in Apison and Bradley County made a bow tie of transmission towers there. The same tornado also killed at least 18.

The strong Bridgeport tornado took out much of TVA's North Alabama power towers and killed at least one person. In all, more than 200 power towers were damaged in the storms. Each tower is 120 feet to 150 feet tall and weighs 20,000 to 30,000 pounds, Martocci said.

Grid holes

In Bridgeport, the Hardee's Restaurant was a gathering spot for some hungry and frustrated people.

On Monday, one man was so angry about still not having power at home that he wouldn't sit with a group of neighbors whose power had just recently been restored. He strode out of the restaurant.

And Herschel Smith, whose power came back on Sunday, said he had to throw out everything in his refrigerator.

"But we know we're lucky," he said, because there are hundreds in the region who lost homes or loved ones.

Several miles south on County Road 255, Corky Childs was trying to find his barn roof.

Looking across a field, he paused to study a concrete slab and lots of litter - all that remained of a house he'd built and sold some years ago.

"This is just hard to believe," he said, pointing to a tractor-trailer that had been carried from the yard across the street and lay twisted, upside down in the side yard of his former home.

On the hill above, electric-line repair crews from Southern Electric in Mississippi restrung street power poles for North Alabama Electric Cooperative, headquartered in Stevenson, Ala.

Martocci said TVA presently had no cost or time estimate for its quick-fix reroutings or for the rebuilding of the North Alabama transmission system. She said the utility would continue gradually to restore power community by community before trying to get power to heavy, direct-served industries.

TVA has restored power to all but eight of the 128 distributor connection points, she said, including utilities in Jackson and DeKalb counties of Alabama.

During the outage, TVA also donated 10,600 ready-to-eat meals to North Alabamians.

Huntsville has been the largest city with no power from TVA.

"We had no damage from tornadoes, but we got the damage of no power," Huntsville Mayor Tommy Battle said Monday, noting that 50 to 60 percent of the city's residential and retail power was back online.

"We're watching now for the next step, which is bringing on heavy industry back on," he said. "Nobody's ever pleased to go through what we've been through. Living without power is a wake-up call to most people. But we feel TVA fulfilled their part of the bargain by working hard 24/7 to get us back into operation."

The double hit

TVA is taking a double hit from the storms.

While the utility foots the bill to repair the lines, its income could be pinched. TVA can't produce or sell power at normal levels and with normal load flexibility until the repairs make the transmission system strong again.

Carried in wave after wave of storms Wednesday, the fierce tornadoes bent TVA's power towers and all three reactors at Browns Ferry Nuclear Plant and the power generating units at Widows Creek Fossil Plant automatically shut down because there was nowhere for the power to go.

When Browns Ferry lost power, it also lost cooling circulation pumps. The design of Browns Ferry is similar to the one of Fukushima Dai-ichi in Japan, the nuclear plant that was severely damaged by March's earthquake and subsequent tsunami.

Unlike Fukushima, Browns Ferry's diesel back-up generators did not fail, and they began operating normally to circulate cooling water in the reactors and in the pools where the spent radioactive fuel rods are stored.

On Monday, Martocci said Browns Ferry cooling operations continued under generator power, and the plant was being lit with the added assistance of two 161,000-volt power lines. She said TVA expected to begin the process of switching from generator-powered cooling to grid electrical-power cooling late Monday.

But she said the plant won't be restarted to generate electricity until the transmission system is sufficiently repaired to transport power away from the plant.

TVA Chief Operating Officer Bill McCollum said TVA is a long way from completing the work ahead.

"Just like homes that were damaged take time to be rebuilt, repairing the transmission system will be a lengthy process."

Contact Pam Sohn at psohn@timesfreepress.com or 423-757-6346.