TVA says transmission service requests have risen 11-fold

By the OGJ Online Staff

HOUSTON, July 24, 2001 – Tennessee Valley Authority, under pressure to open up its huge transmission system to use by private concerns, said it shouldn’t be blamed for creating bottlenecks for wholesale electricity transactions.

Wai-Ran Wu, a transmission security specialist, told an internal TVA publication the federal power agency finds itself simultaneously carrying loopflows– unscheduled power flowing over the system – at the same time it’s unfairly accused of being a bottleneck to the transmission of power in the Southeast.

He said generators are being built today without adequate transmission, creating enormous competition for use of the transmission system and an exponential increase in requests for transmission service. This year TVA is projecting 275,000 requests for transmission service, up from 250,000 requests in 2000, and 24,000 requests in 1997.

Earlier this year, the North American Electric Reliability Council ((NERC) said heavy north-to-south power transfers occurred at the Tennessee Valley Authority interface in 2000 spurred by extremely high temperatures in the South and cooler than normal temperatures in the North. As a result, the nonprofit organization which engages in planning of the bulk power system said the Eastern Interconnection interface was loaded “well beyond its calculated transfer capability”

Based on transmission reservations for summer 2001, NERC predicted the interface will experience heavy flows again this summer, which will lead to a number of transactions being interrupted and potential emergencies.

The interrupted business deals resulted in lost business for the merchant generators and a need to replace the transaction with higher priced power for the buyers, and in some cases, interruption of interruptible customers, NERC general counsel David Cook testified before the Senate Committee on Energy and Natural Resources earlier this year.

“What do not show up are the transactions that merchants or marketers decided not to engage in because of the likelihood they would be interrupted,” he said.

In the Southeastern Electric Reliability Council (SERC), which includes TVA, NERC said recent generation additions in the southern subregion have raised stability concerns and these concerns “could limit generation output under certain conditions.”

In addition, Cook said, “We have seen entities improperly leaning on the Interconnection, causing unscheduled and unmanageable flows and potential voltage problems.” He said some entities have made the economic judgment it is less costly to them to violate the rules than to follow them. But he said it would be a mistake to relax reliability rules to allow higher flows.

The TVA’s Wu said all utilities can find themselves unable to move power through their systems. Other utilities in the Eastern Interconnection are side paths to transmission, compared to TVA, which is the prime path for north-south power moves. Power follows the path of least resistance, not necessarily the intended track.

Because TVA has a strong system, “power flows to us, scheduled or not,” he said. TVA worked with the Electric Power Research Institute and others in the industry to develop a methodology to track actual system flows. Now TVA officials said they are working to win industry acceptance of the methodology, so owners of the lines actually carrying the power will be paid.

Terry Boston, executive vice-president, said TVA has added 700 miles of new transmission since 1995, more capacitors to improve voltage control, and new computer tools to trace power flow more accurately.

The TVA system can accommodate about 40,000 Mw of extra power on its system without risking reliability, he said. If demand exceeds transmission capacity, TVA will curtail transactions to preserve reliability, said Boston.

Someone with a financial interest in transactions that TVA curtails might view TVA as a bottleneck, Boston said. However, if TVA didn’t curtail when the system is close to overloading, he said it would be risking blackouts for the Tennessee Valley and the entire Southeast.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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