Terrain Effects on Overhead Line Vibration
This white paper examines how varying terrains impact overhead line vibrations and outlines AFL's terrain categories to simplify selection and improve line design for diverse environmental conditions.
The terrain across the United States widely varies and every overhead lines project will have its own considerations and challenges. One aspect of line design – where terrain plays a crucial role – is the effect it has on overhead conductor and cable motion.
In terms of conductor motion control, laminar flow is the main source of issues. Open, flat terrain has been found to exhibit both the highest likelihood and severity of vibration damage. The reason for this is that overhead line vibrations are caused by vortex shedding in the presence of smooth and steady wind. Trees, hills, buildings and similar features introduce turbulence and will break up the laminar flow of the wind. Without these features, vibrations are likely to occur.
To make the terrain category selection easier for the line designer, AFL separates terrain options into three wind speed categories:
- 15 mph (Normal Terrain)
- 20 mph (Flat Terrain)
- 25 mph (Water/Canyon Crossing)