Reducing the effects of lightning in cogeneration plants

Georgia Transmission Corporation (GTC) serves the Weyerbaeuser Flint River Mill in Oglethorpe, GA, with a new, nondedicated 115 kV radial-transmission line connecting from the North Americus substation with a tap to the South Oglethorpe substation. The Flint River mill is a cogenerator with a single 46.6 MVA steam-turbine generator fueled by biomass. The line suffered from repeated outages, primarily due to lightning strikes, since the day it was commissioned. As a result, increased attention and concern has been given to the problems associated with resultant voltage fluctuations and momentary outages in the mill. More effort has been placed on service reliability and tracking these fluctuations and outages. Several lightning engineering programs have been studied. In particular, the Windows-based Lightning-Protection Design Workstation, developed by EPRI, was investigated. The program was used to provide a comparison of pole-line configuration, arrester usage, and static protection as would relate to power outages. It calculates the lightning performances of overhead transmission lines and indicates what, if any, flashover design improvements are required to reduce iightning-caused outages. A further investigation involved the use of a computer-based scope with the ability to see storms over 483 km (300 mi) away. Early detection of storms with the potential to produce strikes on the mill site or the transmission line will allow the mill to take the necessary steps to operate independently from the electric utility company until the thunderstorm subsides