| 摘要 |
PURPOSE:To prevent the lowering of shielding effect in a power cable by connecting a direct current to both ends of a metal shielding layer thereof to detect the deterioration in the shielding layer from the direct current flowing through the metal shielding layer. CONSTITUTION:A DC power source 16 is connected to both ends of a metal shielding layer 12 of a power cable 10 through an ammeter 14 which detects the direct current I flowing through the shielding layer 12. In operation, when water is contained in the shielding layer 12, the contact resistance between laps rises to reduce the direct current I thereby enabling the measurement of the degree of deterioration in the shielding layer 12. This can prevent the lowering of shielding effect of the power cable as early as possible.
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