| 摘要 |
PROBLEM TO BE SOLVED: To make detectable impurities or the like in the boundary surface of an insulating material in a non-destructive manner by detecting a change in the boundary surface between solid insulating materials according to the change in the frequency characteristic of dielectric characteristic (tanδ) measured by means of the materials. SOLUTION: This non-destructive detection method of impurities such as decomposition residue of cross-linking agent applied to the boundary surface of insulator in a connection part of a CV cable is carried out by measuring the dielectric characteristic (tanδ) of a sample 11 composed of insulation sheets 12, 13 forming boundary surfaces to be measured by means of a dielectric spectrum measurement apparatus equipped with a measurement electrode 15. When there is nothing as impurities layer 14 of the boundary surface, no peak is observed in spectrum 1 after the measurement of frequency characteristic of the dielectric characteristic (tanδ) under specified conditions. However, when there is such the impurities layer 14 as cumiyl alcohol, acetophenon or process oil, resulting from a CV cable production process, a significant difference in spectrum such as a tanδpeak difference at the frequency range corresponding to the materials can be recognized.
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