Transmission lines are supported by large wood, steel, or concrete structures or poles. There are a number of common construction methods used for transmission towers depending on the weather the transmission line will be subjected to the topography of the land and the amount of right-of-way available to place a tower. Concrete Poles Picture

Single poles are useful for small transmission lines with lower voltages that do not require large clearance between wires and the ground or where the right-of-way area is limited. Single pole concrete and steel structures are being used more and more as right-of-way availability decreases and the cost of large wood poles increases.

H Frame Picture Lattice Tower PictureMany larger transmission lines use multiple wood or steel pole structures for support. The H frame is a standard transmission line construction seen in many parts of the country and gets its name from the H created by the poles and cross arms. Large steel frames, sometimes referred to as lattice towers, come in many shapes and sizes and offer the most stable support for large high voltage transmission lines.

Underbuild PictureA common construction method in many utilities is to place a lower voltage distribution circuit underneath the transmission circuits, thereby using a single structure for both transmission and distribution circuits. This is known as underbuild because the distribution line is located underneath the transmission line.