They consist of a steel core in a form of one or more twisted steel wires, surrounded by one or more layers of hard aluminium wires EN AW-1350 or EN AW-1370. For protection against corrosion, core wires are covered with protective coating, usually in a form of a zinc layer applied galvanically. In addition, in order to prevent from corrosion, if a cable may be exposed to the effects of atmospheric factors, spaces between wires are filled with special grease resistant to increased temperature. In operating steel and aluminium cables, mechanical load is transferred by both steel core wires and conductive aluminium layers. Hence, the strength of these cables while maintaining a sufficiently low weight allows to suspend them in longs distances from each other (even by a few kilometres) pillars, which in turn allows to significantly reduce the number of necessary supporting structures.
Selected products safety data sheets:
AFL-1.7 cables (AL1-ST1A) based on PN-EN 50182 MT-19-01-16
AFL-6 cables (AL1-ST1A) based on PN-EN 50182 MT-19-01-16
AFL-8 cables (AL1-ST1A) based on PN-EN 50182 MT-19-01-16
A very interesting example of steel aluminium cable with optimized for energy loss structure and carried out based on the standards of the Polish Energy Networks is a hot cable of 400kV line with the mark of 408-AL1F_34-UHST PSE-SF.Line400kV.4PL-2013v2 MT-22-12-15. This cable consists of a core made of 7 steel wires with ultra high galvanised strength, on which 3 layers of hard aluminium wires are imposed, and the last layer is made of two previously released trapezoidal wires.