500 kV Lattice Tower Development for Energy Gateway

PacifiCorp began a broad expansion in 2007 of its main grid transmission system in the western United States through a program called Energy Gateway. This ongoing effort will add more than 1900 miles of 230, 345, and 500 kilovolt lines to PacifiCorp's transmission system. One key element of this transmission expansion is the development of 15 different 500-kV steel lattice towers to date with a variety of tangent, running angle, transposition and dead-ends in both single and double circuit configurations. A broad overview of the development and use of this family of 500 kV towers is detailed herein. The tower family was designed for reliable and cost-effective line construction through the wide ranging elevations, terrain, geology and climate of Utah, Idaho and Wyoming. Electrical and mechanical requirements and National Environmental Policy Act (NEPA) permitting were significant drivers for the tower design. Tower development is truly a global process. Energy Gateway towers were designed in Texas and Mexico. Full scale load tests were performed on nine towers at five test facilities in Brazil, South Africa and India. Proto-type testing occurred in Mexico during design and in Turkey with the first tower purchase. Ongoing construction of the Mona-Oquirrh 500 kV line has completed installation of more than 100 towers by June 1, 2012, with energizing scheduled for mid-2013.