Aging of Conductors
ACSR lines reach the end of their service life due primarily to corrosion from industrial pollutant and salt sea air. There are two corrosion processes that effect the useful life of ACSR lines:
a. Corrosion of the steel core bundle
This happens because the zinc galvanizing corrodes leaving the steel core exposed to the environment. Over time the cross section of the steel core bundle is reduced through pitting corrosion and the line can fail due to loss of torsional ductility and/or mechanical strength.
b. Corrosion of the aluminum strands
Once the galvanizing is lost and the unprotected steel is exposed to the aluminum conductor, corrosion of the aluminum can begin. In the presence of a suitable electrolyte, aluminum becomes the sacrificial anode and oxidizes in preference to the steel because it is a more electrically active metal. In latter stages of corrosion the loss of aluminum conductor increases resistance creating hot spots on the cable. This can cause the aluminum to melt and the conductor to fail. View Diagram of Corrosion