UF helps Florida utilities assess impact of wind on power lines

August 18, 2008

GAINESVILLE, Fla. — With Tropical Storm Fay bearing down on Florida, thousands of residents are likely to be faced with power outages that are both disruptive and costly.

To find ways to cost-effectively reduce the number of blackouts that historically accompany tropical storm or hurricane landfalls, University of Florida researchers are engaged in a major collaboration with Florida’s utility companies.

The Hurricane Hardening Project is examining how hurricane winds affect both underground and overhead power lines. The project is also seeking the best ways to minimize tree-related outages and other potential threats to electric infrastructure in an effort to speed the restoration process in the aftermath of storms.

“Preparing for storms requires cooperation from many groups and organizations,” said Matthew Carter II, chairman of the Florida Public Service Commission, which initiated the project. “We are pleased that the University of Florida is fostering cooperation by working with Florida’s utilities on research to strengthen the state’s electrical grid.”

Researchers and utilities are studying the impacts of moving lines underground and also examining the possibility of strengthening existing overhead systems as a cheaper alternative, said Mark Jamison, director of UF’s Public Utility Research Center, which is coordinating the hurricane hardening effort.

This innovative research has resulted in an experimental computer model that may be helpful in assessing the costs and benefits of burying power lines.

“People need to know the costs and benefits to decide whether it’s worth moving lines underground,” Jamison said. “Once we have this information, customers, policymakers and utility companies can make sound choices.”
Researchers have also examined four cases in Florida where utilities have converted overhead lines to underground. Their main conclusion: Moving existing overhead lines underground is costly and usually not justified solely by the economic benefits but rather by other benefits that are difficult to quantify such as aesthetics.

That said, burying utility lines in some communities may have advantages, especially in the case of new construction, when underground lines can be included in the development’s planning process.

People often view underground power lines as a solution to storm-caused outages. But they are not the cure-all they appear to be, Jamison said. Underground facilities are more prone to damage from flooding, storm surge and erosion, which can lead to increased costs and repair times, he said.

To obtain more detailed information on the damage hurricane winds cause to overhead lines, project partners have installed 50 wind observation stations on existing or specialized utility poles along the coast of Florida. Instruments on each station collect wind speed, wind direction, barometric pressure and other data.

Kurt Gurley, an associate professor of civil and coastal engineering, has tested the wind stations using the UF hurricane simulator to ensure their electronics can withstand hurricane force winds and driving rain. He will also help interpret the data supplied by each station.

“The wind monitoring network in Florida will provide the detailed ground-level hurricane wind behavior that is badly needed by engineers working to better understand the ways that the power distribution infrastructure fails,” Gurley said.

The National Oceanic and Atmospheric Administration and utility companies will receive this data from the stations in real-time, and NOAA will use the data to create wind field maps.

Once the hurricane passes, utilities will mobilize teams of first-responders to assess where and how the electric system failed. Using the NOAA wind maps, they will match wind speeds with damages on the ground. This “forensic data” will then be analyzed to determine which hardening strategies work best. “If the power distribution system failed, we will be better able to analyze the damage and determine why the damage occurred,” Gurley said.

As part of the Hurricane Hardening Project, utility companies are also studying ways to improve their vegetation management programs. They maintain a regular schedule of trimming to keep lines clear and routinely monitor critical distribution facilities.

Researchers and utilities in this project are partnering with WeatherFlow, a company that develops, manages and installs wind measuring devices. Quanta Technologies conducted the research on underground lines and developed the computer model.