<P> Aluminium conductor steel - reinforced cable (ACSR) is a type of high - capacity, high - strength stranded conductor typically used in overhead power lines . The outer strands are high - purity aluminium, chosen for its good conductivity, low weight and low cost . The center strand is steel for additional strength to help support the weight of the conductor . Steel is higher strength than aluminium which allows for increased mechanical tension to be applied on the conductor . Steel also has lower elastic and inelastic deformation (permanent elongation) due to mechanical loading (e.g. wind and ice) as well as a lower coefficient of thermal expansion under current loading . These properties allow ACSR to sag significantly less than all - aluminium conductors . Per the International Electrotechnical Commission (IEC) and The CSA Group (formerly the Canadian Standards Association or CSA) naming convention, ACSR is designated A1 / S1A . </P> <P> The aluminium alloy and temper used for the outer strands in the United States and Canada is normally 1350 - H19 and elsewhere is 1370 - H19, each with 99.5 +% aluminium content . The temper of the aluminium is defined by the aluminium version's suffix, which in the case of H19 is extra hard . To extend the service life of the steel strands used for the conductor core they are normally galvanized, or coated with another material to prevent corrosion . The diameters of the strands used for both the aluminum and steel strands vary for different ACSR conductors . </P>

The function of steel wire in acsr conductor is to
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