NEXT MEETING ___________________________________________________

Monday, May 21, 12:00 noon

Cellar Restaurant at Union Square

Downtown, Chattanooga

Barry Gore, Manager, TVA O&M Projects

Coronal discharges that occur around high voltage transmission lines and substations are not only a nuisance but they can cause severe damage to electrical equipment, especially non-ceramic insulators. It is thus important to detect the location of these discharges and take effective measures to minimize their affect. Traditionally, such detection was performed at night because corona discharges appear as a bluish ultraviolet light that would otherwise be overpowered by sunlight. But without daylight, it is difficult to determine the location of a discharge with respect to the surrounding area.

Enter the "day-time corona" or "DayCor" camera. It is a devise that uses a very narrow bandwidth filter to focus on the corona emission spectra and add just sufficient "daylight" to provide a perspective of where the discharge is occurring. TVA has recently begun to use such cameras to survey its many miles of transmission lines and myriad of substations.

Barry Gore, Manager, O&M Projects for TVA's Transmission Operations and Maintenance organization will describe to us how this camera works and how it is applied in the field. He will also demonstrate the operation of the camera. Barry is responsible for managing a wide variety of development and application projects as well as scheduling and implementing new technology such as the DayCor cameras.

FUTURE MONDAY MEETINGS ______________________________________

May 28: No meeting – In observance of Memorial Day

June 4: "SWAT Jobs and Porto-Sags -- Peeling the Power Quality Onion"
- Arshad Mansoor, Engineering Manager, EPRI-PEAC, Knoxville

June 11: "TVA's Regenesys Project - Installation of a 12 -Mw Flow Battery
for Peak Shaving and Load Shifting". - Joe Hogland and Mick Ray - TVA

June 18: "The Electric Power Industry - Its History and Likely Future".
Terry Boston - TVA

June 25: "Intelligent Transportation Systems"
Dr. Rekha Pillai - Oak Ridge National Lab

OUR LAST EVENT – May 14 _______________________________________

SF6, sulfur hexaflouride, is a colorless, odorless, noncombustible compound with low toxicity, slightly soluble in water. One of its main uses is as a dielectric gaseous insulator for electrical equipment such as transformers, circuit breakers, and other electrical switchgear.

SF6 is viewed by the engineering community – and especially the electrical industry- as a very useful compound. It is extremely stable and has the property of quenching electric arcs, as well as good heat transfer properties. SF6 is currently used in many other applications such as in windows (to reduce solar radiation through window panes), tires, metallurgy, and those springy heel inserts for tennis shoe soles. It has strong electron capture properties due to its electronegativity. Since the 1970’s, its use in electrical switchgear has increased, until leveling off in the late 1990’s.

To the environmental community, SF6 poses a threat because of its persistence in the biosphere and potential to contribute to the greenhouse effect. Its presence in the biosphere has increased two orders of magnitude since 1973. SF6 is a very effective absorber of IR energy, and levels now seen could increase global warming 0.1%. Its use to replace oil in transformers increased until 1997, when voluntary SF6 reductions were requested. SF6 is about 3600 times more absorbent of IR energy that CO2. It’s structure would make it very persistent and long-lived in the atmosphere.

SF6 inventories are monitored by weighing the gas cylinders, and recycling equipment is used to dehumidify and return the gas to the equipment rather than venting to the atmosphere, as was done in the past. A 40/60 mix of N2/SF6 has been proposed for future use but the efficiency of this mixture is about 20% less, making arcing more likely.

EPA is coordinating a voluntary reduction effort (see voluntary standards program for handling SF6 on the EPA website (http://www.epa.gov/highgwp1/sf6/). It is now possible to monitor and correct leaks and inventory SF6 usage. The decomposition of SF6 to toxic S8F10 makes the older practice of "whiffing" the gas for the smell of rotten eggs a very bad idea. It is said one whiff of S8F10 can knock an elephant down due to it’s high toxicity. Any solid byproducts from an equipment failure involving arcing or combustion must be treated as hazardous material and proper disposal methods must be followed.

Currently, there are no effective replacements for SF6 in many applications, so industry is increasing it’s monitoring activities, replacement practices, and standards for handling and disposal of SF6.