Damage investigation of the aged aluminium cable steel reinforced (ACSR) conductors in a high-voltage transmission line

In order to evaluate the damage of the 26-year-old ACSR conductors of the 100 kV Zhu–Xie transmission line in Tongling, Anhui province, China, the conductors across the #11 and #12 towers were studied via morphological observation, metallurgical analysis and individual wire tensile strength (IWTS) test, especially for the conductors under the vibration dampers and the strain clamps. The results show that the outer Al strands of the conductor under the vibration damper and the strain clamp are mainly subject to the scraping damage by the aluminum armour tape and the adhesion/abrasive wear injured by the aluminum armour tape and the other Al strands. As for the inner Al strands, the main damage mechanisms are of the adhesion/abrasive wear and the propagation of the fatigue cracks originated from the wear surface. For the steel core strands, only the zinc coating is partially destroyed, but the steel cores are survived. After 26 years running, the average IWTSs of the outer/inner Al strands decrease more or less, however, the IWTS of the steel core strands is almost not changed. The aged conductors are still in a good condition, but more intensive inspection and maintenance is suggested.

► Scraping of the outer Al strands by the aluminum armour tape.
► Adhesion/abrasive wear and propagation of the microcracks in the Al strands.
► Structural damage of the steel core strands.
► Shift and rotation of the contact marks on the inner Al strands.
► Mechanical property degradation corresponds to the damage of the aged conductors.