| Popis: |
The topography of the terrain plays a major role on the galloping of the conductors in a transmission line, especially in complicated terrains. In the present work the authors try to develop relatively new approach to use the Geographic Information Systems (GIS) data of a terrain and converted it to an accurate 3D terrain model that is suitable for carrying out computational fluid dynamics (CFD) analysis. Further, the newly developed approach will be used to evaluate the contribution of the terrain to the collapse of a high voltage transmission tower near Saurdal a town in north-western part of Norway. The first part of the article describes in detail each step involved in the conversion of GIS data to 3D computed added design (CAD) model. Initially, the data of the accident site including the location details of the collapsed tower was obtained, this information was then used in google earth pro software to access the GIS information of the region around the collapsed tower. Then SketchUp software was employed to convert the GIS to modeler data, and finally Rhinoceros 3D was used to get the final 3D CAD file. The entire developed process was explained through the cases study of Saurdal. Actual weather data such as gust speed, gust direction, temperature, and snow cover on the terrain during the time of accident was obtained from five different weather stations was used to carry out a steady state CFD analysis. The results indicated a strong relation between terrain complexity, wind speed, and wind direction. The terrain was able to modify the local wind direction and local wind speed. For the Saurdal case the simulation results indicated that approximately 30 degrees deviation in angle of attack (crosswind) was observed in then local wind direction heading towards the collapsed tower. The terrain also contributed to increase in approximately 30–40% in local wind velocities compared to free stream, especially on higher altitude lands of the terrain. Finally, for the Saurdal incident, the results indicated that the combination of high strength ESE gusts, and terrain induced crosswinds may have resulted in the collapse of the tower. |
