Impact of conductor assembly indentation on the fatigue properties of copper power cable wires

Abstract

The production process of high voltage power cables includes the assembly of the conductor, which is composed of different layer of independent wires wound in helixes of opposite pitch for each subsequent layer. Each wire, which has an initial constant round cross section and is close to annealed conditions, is wound around the previous layer and the assembled layers are passed through a calibrated die which compacts the wires together. This process creates periodically spaced indents on the inner side of the wires and work hardens the material in the indented sections and their immediate proximity. Both the local and global strain distribution related to static loads as well as the fatigue properties of the wires are impacted by such process and its consequent geometrical and material inhomogeneities. In this work, strain-control fatigue results of copper conductor wire are presented. The non-uniform strain distribution caused by the inhomogeneities inferred by their manufacturing process is investigated with the means of digital image correlation. The "indentation" process is modelled with the use of explicit finite elements and the deformation of the virtual specimen obtained is compared with the experimental results.