Wet-Snow Accretion on Overhead Conductors: Experimental Study in a Climatic Wind Tunnel
摘要
The estimation of ice loads is essential for assessing the structural reliability of transmission lines. A probabilistic approach requires the numerical simulation of ice load time histories, derived from meteorological data using empirical models available in the literature, such as the Makkonen model. By analyzing annual extreme values, the risk of structural failure can be quantified for a given probability of occurrence. Ice accretion on conductors can result from various processes, depending on the prevailing meteorological conditions. These processes are typically classified into in-cloud icing, freezing rain, and wet snow accretion. Among these, wet snow accretion is particularly critical due to its relatively high probability of occurrence at altitudes above 600 m, combined with the considerable masses of ice it can generate. To improve the understanding, validate, and extend existing ice load models, a series of experiments was performed on a conductor specimen in the Jules Verne climatic wind tunnel at the CSTB facility in Nantes, France. The experiments focused on wet snow accretion, systematically varying key ambient parameters. The liquid water ratio of snow particles plays a crucial role in determining whether the accretion is light and dry or, conversely, heavy and wet. The first set of experiments investigated the accreted ice mass and shape on a non-rotating conductor for different snow qualities, ranging from drier to wetter snow. Subsequently, the effect of axial rotation of the conductor was examined under the most unfavorable snow condition. Finally, the influence of wind direction on snow accretion was also evaluated and discussed.