Metal Magnetic Memory-Based Electromagnetic Non-Destructive Evaluation of Steel-Core Damage in UHV ACSR Conductors

Internal steel-core damage hidden within aluminum conductor steel-reinforced (ACSR) compression components may threaten the mechanical integrity of ultra-high-voltage transmission lines. This laboratory study evaluates metal magnetic memory testing (MMMT) responses to artificial discontinuities in seven-strand ACSR steel cores under four nominal lift-off distances, two nominal orthogonal specimen orientations, and a simplified aluminum-tube-covered condition. One intact specimen and five artificially damaged 1 m specimens were preloaded to 16 kN for 2 min, unloaded, and scanned using the normal magnetic-field component recorded by Channel 1 of a TSC-1M-4 detector. Quantitative descriptors included peak-to-peak amplitude, abnormal-field width, maximum gradient, and short-term within-specimen repeatability. At 5 mm lift-off, peak-to-peak amplitudes ranged from 18.7 to 91.4 A/m. Across three repeated repositioning scans, amplitude coefficients of variation ranged from 0.83% to 8.04%. Relative to 5 mm, the descriptive mean amplitude loss reached 66.3%, 81.9%, and 89.8% at 20, 30, and 40 mm, respectively. Orientation changed signal polarity and amplitude in a specimen-dependent manner. Anomalies remained visible under the aluminum-tube configuration, although covering and effective lift-off effects could not be separated. The results provide preliminary laboratory evidence for further evaluation of MMMT as a screening approach; the reported feature values are not field detection thresholds.