sealPurdue News

March 2001

Engineers will demonstrate new system
to prevent power failures

WEST LAFAYETTE, Ind. – A team of engineers led by a Purdue University researcher will demonstrate a new system in April that aims to avert power failures by automatically adapting to the daily fluctuations in electricity consumption.

The system might be especially helpful in easing problems associated with electricity shortages and utility deregulation. It would precisely predict and monitor electricity consumption for each customer from one hour to the next, also making it possible to charge higher rates for those placing the greatest strain on the power grid during times of peak demand.

"Our approach is to make the behavior of the customers sort of amenable to the market forces," said Lefteri Tsoukalas, a professor of nuclear engineering at Purdue.

Computerized systems are now capable of precisely gauging how much electricity a customer is using from one hour to the next, even to the point of measuring the changing consumption of individual home appliances. Some customers consume power in extremely predictable patterns, which makes it easier for utilities to manage electrical distribution. But other customers are less predictable, complicating efforts to keep the system from crashing.

"When there is a shortage of electricity and one customer wants to heat up his Jacuzzi, he should be paying more," Tsoukalas said. "An essential element of our approach is to modify the behavior of customers for the well-being of the entire system."

Work on the new system, called TELOS, for Transmission Entities with Learning Capabilities and On-Line Self-Healing, is headed by Tsoukalas. He is one of 23 researchers in the Consortium for the Intelligent Management of the Electric Power Grid.

TELOS is said to be a "self-healing" system because it automatically adjusts to new conditions. It is designed to prevent power failures by anticipating the quickly changing demands of industrial, commercial and residential electric customers. The system would accurately predict power needs for the coming day and then automatically meet those demands by better managing electricity distribution and supplementing the grid with power from small natural gas or diesel generators, which would kick on when needed.

Such an automated system would enable sophisticated control of small sections within a service area, which is a sorely needed innovation because changes in electrical demand can vary drastically from one part of town to another.

"We want to endow the grid with certain self-regulation capabilities," Tsoukalas said. These small sections would be called local area grids, or LAGs. During times of peak demand, TELOS would combine LAGs so that customers in one area who were expected to increase their consumption over the next hour might be offset by customers in another LAG who were expected to reduce their consumption during the same time frame. The predictions would be made using computer databases containing a history of each customer's electrical consumption.

Partitioning the power grid into LAGS would enable a utility company to better predict and avert an impending overload within the system. Presently, damage to a single substation in the grid can trigger a domino effect, a cascading series of equipment failures leading to a widespread power failure. Isolating problems to a particular LAG would, therefore, prevent widespread power failures.

"At the heart of our approach is a model of the electric power system that focuses on customers," Tsoukalas said. "We start from the customer end of the system to determine how much power we will need to meet the demand of all these customers."

Members of the consortium include engineers and graduate students from Purdue University; Commonwealth Edison Co., a utility serving northern Illinois; the University of Tennessee; Fisk University; the Tennessee Valley Authority, the nation's largest public power company; and the Electric Power Research Institute, an organization of electric utilities.

TELOS will be demonstrated during a public meeting of the consortium, tentatively scheduled for April 2, at the University of Tennessee. Research findings show that TELOS would be effective in better controlling the flow of electricity during times of peak demand, such as a summer heat wave.

The findings are based partially on the analyses of energy-consumption profiles of customers in the Chicago-area city of DeKalb, Ill. DeKalb was chosen for the research because it contains a wide range of users, from a university to industrial and residential neighborhoods.

"Telos" is a Greek word meaning purpose, or the where and why of things, says Tsoukalas, who specializes in "neurofuzzy systems." Such computer software is designed to think more like people by learning from experience and using the "fuzzy logic" of human reasoning.

Because electricity cannot be stored in large amounts, it is extremely difficult to maintain a smooth flow throughout a power grid that is made up of diverse users, some of whom vary their consumption considerably on a weekly, daily or even an hourly basis. The supply must be balanced constantly to meet the changing demands, which can fluctuate greatly in various sections of the service area, Tsoukalas said.

Fuzzy logic systems work by evaluating the overall accuracy, instead of the fine precision, of a solution to a problem. The human brain uses the same sort of approach to make effective decisions.

"We adjust the thermostat in the room not by calculating precisely what the perfect temperature would be, but basically by deciding that it's comfortable or uncomfortable," Tsoukalas says. Another example of fuzzy logic can be found in language. Although human vision can literally distinguish more than a million shades of colors, languages do not contain a million words for colors.

"We would be overwhelmed if we didn't have the ability to summarize," he says.

In a similar way, mathematical models can be used to predict future changes in electricity demands by evaluating the present usage in the context of environmental factors and historical patterns. Such a system might reason along the following lines: "The weather is getting warmer, it's the middle of summer and the humidity is increasing. Therefore, when historical consumption patterns are considered, we should expect the demand to rise by so much in the next hour."

Utility company workers currently perform the prediction role. They begin the day by trying to anticipate what the power demand will be over the next several hours in the entire grid. However, different parts of the service area sometimes have their own distinctive microclimates that affect electricity use. Therefore, engineers are aiming to break the service area into LAGs.

TELOS is scheduled to be completed by the end of 2001 and to be operating in 2003 on a trial basis in the Commonwealth Edison and Tennessee Valley Authority service areas. If it works, TELOS will be available for use on a national level, Tsoukalas said.

Source: Lefteri Tsoukalas, (765) 494-0198;

Writer: Emil Venere, (765) 494-4709;

Purdue News Service: (765) 494-2096;

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