Keeping It Close: A Composite Solution to Rebuilding a 69 kV Line

There are several critical customers located in Southern Maryland Electric Cooperative, SMECO territory. Until recently, one customer had been served by Potomac Electric Power Company, PEPCO, up until 2012 when the feed to the facility was purchased from PEPCO by SMECO. The feed to this customer is a radial, 69-kilovolt line dating back to the mid 1940s. When SMECO purchased the line, it was in need of extensive repair. A significant section of the line needed to be rebuilt entirely. The line rebuild presented numerous challenges that had to be addressed, including: The only back up source for the line is onsite generation that cannot support the entire facility at once. Extended outages were not an option and were limited to weekends in late fall and early spring. The line would have to be rebuilt while the existing line remained energized. The railroad, parallel to the line, had been converted to a hiker/biker trail with significant pedestrian traffic. The line traverses part of the Mattawoman Creek watershed, which is recognized to be a critical area by the EPA. Given the critical nature of the line and surrounding limitations, SMECO realized that standard construction practices would not be practical within the project’s parameters. In conjunction with the project engineer, Booth & Associates, SMECO evaluated several options for rebuilding the line and determined the most practical option was to rebuild the line using composite poles on an offset centerline 10 feet from the existing centerline. Composite poles have a life expectancy comparable to steel poles, and the lightweight nature of composite material allowed the contractor to use lighter construction equipment resulting in no significant damage to the bike path. The base sections were set first, and the pole tops were set using only the material handler on the contractor’s bucket trucks. Only two outages under two days each spread over two weekends were required to complete the line cutover and retire the old line.