Bare cables for aerial lines

Bare cables for aerial lines

Depending on its application, the range of bare cables for aerial lines can be divided in phase and ground wires conductors, which consist mainly of aluminium cables, aluminium alloy and aluminium conductor steel reinforced cables. Still, the range also includes copper cables, conventionally supplied for the Portuguese Electricity Company - EDP – lines. Copper is gradually being replaced by aluminium on aerial lines since aluminium is lighter and less expensive.

As the energy consumption has grown, aerial lines assumed extraordinary importance. The need to carry electrical power all over different types of areas forced the development of more robust cables, to overcome difficult paths with higher spans, and ensuring a lifetime of a few dozens of years.

Although having great potential on power distribution, aluminium cables proved to be inadequate in some situations, because of its insufficient mechanical resistance related with low tensile strength, excessive creep and high coefficient of thermal expansion. Therefore, other solutions appeared using wires of different materials, namely, aluminium alloys and galvanised steel wires, as reinforcement elements. Recently, the application of steel wires coated with a thin layer of aluminium allowed obtaining cables more resistant to corrosion when compared with those having galvanised steel wires.

Basically, aerial bare cables construction consists on wires of one or more metals, stranded in concentric layers with alternating directions. By changing the wires diameter, the number of layers and the wires stranding pitch, when referring to aluminium conductor steel reinforced cables, one can get a variety of designs meeting the requirements of each line, both for transport capacity and all associated electrical parameters, but also for mechanical characteristics required by the installation conditions; maximum distance to the ground, sag, spans, etc.