Study of inspection of wire breakage in aluminum transmission line using SQUID

Taking advantage of the unsurpassed high-magnetic sensitivity of high-temperature superconductor (HTS) superconducting quantum interference device (SQUID), HTS-SQUID-non-destructive evaluation (NDE) technique was applied to detection of single wire breakage in hard-drawn aluminum transmission line (HAL), which was twisted from 19 aluminum wires. While applying AC current of 2.6 mA at 200 Hz to the HAL, distribution of magnetic field gradient above the HAL was two-dimensionally scanned by a HTS-SQUID gradiometer. A periodic pattern was detected along the locus of the broken wire in the distribution from the HAL with wire breakage, while such pattern was not observed in that from normal HAL without wire breakage. These results indicate the possibility of detection of single wire breakage by the magnetic inspection technique.