Effects from downbursts on overhead lines. Meteorological thunderstorm study-climatological, meteorological and CFD analysis

摘要

In February and March 2008 cyclone "Emma" crossed some countries of central Europe and caused severe damages. In very local areas thunderstorms with downbursts were embedded in "Emma" and led to collapses of overhead lines. Downbursts are downward winds with high velocity within a thunderstorm concerning a relative small area. They occur seldom but can have severe effects and are responsible for various local damages on buildings, forests and infrastructure as e.g. overhead lines. In many cases in history, such damages were not brought into connection with downbursts. The Cigre reports 350 and 410 deal with localized high intensity winds. They state that".. .more research is needed to study the interaction of localized winds with supports..." The question arose if the terrain triggered wind speed-up effects. Another question was which wind forces and directions occurred during these events. To investigate the influences of high wind speeds on damaged overhead lines, a pilot study was carried out. Three dimensional wind fields where computed and analyzed regarding to speed-up effects. This paper presents the investigations, climatological aspects as well as CFD case studies (Computational Fluid Dynamics) and shows the amplification factors for the wind speed. The method which was developed in the project can be used for any other region to simulate tendencies of wind speed-up, regardless if they come from downbursts or not. It helps to a better understanding of the reason for wind induced failures.