Adhesion of Wet Snow to Different Cable Surfaces

Cohesion of snow and its adhesion to cable surfaces are the decisive factors for wet-snow shedding from power-line cables. Knowing the adhesive strength of snow is essential to predict when snow will shed and what consequences it will have on the elements of the transmission line. It also appears to be a basic input for simulating wet-snow shedding. Snow adhesion depends on several parameters, among which snow liquid water content and density, and cable surface geometry were examined experimentally. In particular, the adhesion of wet-snow samples to flat surfaces of different roughness, and to stranded cable surfaces was examined in this study. Two series of experiments were conducted to measure shear adhesive strength as well as tensile adhesive strength of snow. Shear adhesive strength was measured with a centrifuge adhesion test device where a snow sample was placed on a beam, which was then rotated with increasing angular frequency until detachment, the angular frequency at detachment being proportional with shear adhesive force and strength. The tensile adhesive tests were carried out with a material test machine on a semi-spherical snow sample. The sample was compressed slowly at a constant speed until it reached a predefined compressive force limit, and then a tensile load was applied until the detachment of snow. The main observations showed that adhesion was strongest for a critical value of liquid water content, that shear adhesive strength was greatest on stranded cable surfaces, and that tensile adhesive strength was weaker on stranded than on flat cable surfaces.