Characterization of an aluminum conductor steel reinforced (ACSR) after 60 years of operation

Abstract

An aluminum conductor steel reinforced (ACSR) extracted from an overhead power line operated in Northern France during more than 60 years was characterized together with a more recent equivalent conductor. Visual inspection, local observation and chemical analysis by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) as well as Raman spectroscopy were used to characterize the microstructure of the strands and to evidence signs of corrosion or potential degradation. Analysis of the grease was done by Fourier Transform InfraRed Spectroscopy (FTIR). The mechanical properties of the strands were evaluated by constant strain rate tensile test at ambient temperature. Hardness was measured as well. Partial oxidation of the steel galvanization layer, degradation of the grease – especially oxidation due to ageing – and atmospheric corrosion pits on the external layer of aluminum strands were evidenced. The mechanical properties of the galvanized steel strands were still in agreement with the requirements of the standards edited in 1955 contrarily to the mechanical properties of the external layer aluminum strands, indicating a potential deleterious effect of the corrosion pits. The tensile strength of the conductor estimated from the mechanical properties of its constitutive strands was slightly higher than the requirements of the standards edited in 1955 and slightly lower than the more demanding requirements of recent standards.