! " # !" !# $%&’ (’ !" !# %)& !" !# %)& !" !# *%&& !+ ,) (’ -- !+ , !# ! "#! ! $ % This paper presents a strain analysis in transmission line cables caused by mechanical vibrations induced mainly by the wind action that can cause the fatigue rupture of the cable. The tests were performed on a test bench that consists of two spans of 9 and 12 meters respectively, and it was built using elements of transmission lines (suspension clamps, insulators, anchoring towers, etc). The vibrations were generated by an electrodynamics shaker. Strains were measured by means of micro!electric strain gauges set in 04 wires of the cross section of the cable at the vicinity of the suspension clamp, which presents severe levels of dynamic stresses. The cable bending amplitude was measured with two laser transducers. The bending amplitude was converted in strain with the Poffenberger!Swart equation. The comparison between the measured strain and the predicted theatrically showed RMS errors of 31% and 48% for axial load levels of 20%UTS and 30%UTS, respectively. Aeolian Vibration, Transmission Lines, Fatigue, Cables. Overhead transmission line cables in their real configuration, installed on top of the towers, are exposed to Aeolian vibrations. These vibrations are a high frequency motion that can occur when a smooth, steady crosswind blows on aerial cables. This laminar wind creates vortices, which are detached at regular intervals on the leeward side, alternating from top and bottom of the cable. The detachments create vertical forces causing the cable to vibrate standing waves generally in high harmonic modes. The cyclic nature of these vibrations can produce fatigue that is, according to the EPRI (1979), the most usual kind of damage produced by the Aeolian vibrations in the transmission line cables and they can also produce damage in other components of the line such as dampers, armour rods and tower members. This kind of damage is more usual in regions where the mechanical behaviour of the cable is restrained such as regions near from suspension clamps, spacer clamps and dampers, Rawlins (1997). Fatigue failure is frequently unexpected and unwarned, with difficult identification and when it happens in transmission line cables, the electric energy supply is interrupted causing blackouts in regions and cities. From the point of view of mechanical behavior, the transmission line cables exhibits a complex behavior because its transversal section is constituted of layers, sometimes of different materials, formed of strands disposed helicoidally. The bending stiffness of the conductor depends on the conductor deformation during the bending process, i. e. it varies not only spatially along the conductor but also 1 !" ##$## " " ##$#### %& " ### during the bending cycle (loading)unloading). This variation influences the conductor displacement and the conductor curvature, which in turn affects the conductor bending stiffness, Papailiou (1997). Therefore, in a same cable the inertia moment of the section can be variable along its axis as a function of the friction level among the strands. This fact can be observed through the abrasion marks in tested cables that are more evident near the clamp and less evident far from it, Poffenberger and Swart (1965). Since forties of last century, many researchers have been made to evaluate the mechanical vibration stresses in transmission line cables for the fatigue analyses. However, the Poffenberger)Swart equation that treats the problem with many simplifications is still recommended for the EPRI to evaluate the cable stress due to mechanical vibrations. Many of the tests used to validate this equation have been conducted comparing the mechanical stress measured with strain gages with the data obtained with the Poffenberger)Swart equation using tests apparatus with rigid cable clamps that normally do not represent the real conditions of transmission lines. In this work, a transmission line cable was tested in laboratory for various levels of frequency and bending amplitude using a test setup that tried to simulate the typical Brazilian configuration of a transmission line with the use of an articulated suspension clamp. Mechanical strains measured with micro strain gages installed on the cable near from the suspension clamp were compared with the ones obtained by Poffenberger)Swart equation. Also, the experimental loop lengths values measured along the tests were compared with the theoretical values.