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SwRI-developed video sagometer helps utilities tap unused power line capacity

For immediate release 

San Antonio, Texas -- August 6, 2002 -- A new device developed by EDM International, Inc. and Southwest Research Institute® (SwRI®) will allow the nation's energy companies to identify the hidden capacity of their transmission lines and significantly increase their power flow.

Government codes require transmission lines to maintain a safe clearance from the ground and other structures, but heat caused by the current flowing through the electrical resistance in the lines causes the lines to expand and sag. Factors such as line tension, weather conditions, and anticipated electrical loads are considered in the design of transmission lines to ensure that the lines have enough capacity to comply with codes. Since most transmission lines are not regularly monitored, the design of these lines is often conservative. As a result, lines are built with power transmission capacity that is rarely used. Energy industry studies show that transmission lines could carry from 5 to 20 percent more power than they currently do.

The video sagometer, developed by SwRI and EDM International, Inc. with funding from EPRI and California Energy Commission (CEC) can be used to monitor ground clearance of power lines in real time.

"The video sagometer is the only technology available that directly measures line clearance, or 'sag,' providing real-time information regarding the capacity of a transmission line," said Glenn Light, director of the Institute's Sensor Systems and Nondestructive Evaluation Technology Department. "This product gives a utility the capability to provide both safe and efficient operation of power lines."

The video sagometer consists of a video camera in sealed, weatherized housing and mounted on any transmission structure or nearby pole. A "target" made of a simple reflective surface is secured to the transmission line. A low-power LED illuminator mounted with the camera generates a beam that illuminates the target at night.

A video signal is sent to a digital processor, which calculates ground clearance. The data can be transmitted in real time by telemetry or logged in a data logger for historical study.

"It allows a utility to transport maximum power during high-usage times in a safe manner," Light said. "It could also change the way transmission lines are designed by reducing some of the conservative assumptions used in their design."

SwRI and EDM researchers developed the video sagometer to integrate directly with the industry's leading line rating software.

For more information, contact Joe Fohn, Communications Department, (210) 522-4630, Fax (210) 522-3547, PO Drawer 28510, San Antonio, Texas 78228-0510.

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