Elastic guided waves are of great interest for the inspection of elongated structures. In practice, analytical or numerical modeling tools are required for a better understanding of the propagation of guided waves, which are multimodal and dispersive, and thereby for the optimization of inspection systems. However, cables are complex structures, helical, multi-wired and highly prestressed. This further complicates the interpretation of measurement. This paper is devoted to the modeling of wave propagation inside seven-wire strands, typically encountered in civil-engineering cables. It gives an overview of recent works, mainly conducted at Ifsttar, in order to account for the helical geometry, interwire coupling and prestress in numerical models. Then, the energy transfer from the central wire to the peripheral ones is investigated by considering an excitation localized into the central wire. The numerical results allow to understand how the energy transfer can decrease with frequency as well as to discover a new compressional mode, of local type, which could be of interest for the non-destructive evaluation or the structural health monitoring of cables.