| 摘要 |
PURPOSE:To prevent a dielectric beakdown accident by detecting the water tree generated in a power cable held under an active wire state, by measuring the DC component in an earth wire current flowing to the earth wire of a power source transformer. CONSTITUTION:The power source transformer 1 charging a CV cable 5 to be measured is insulated from the earth and the DC component in the earth wire current flowed to the earth from the cable through the leakage resistance of the insulator of the transformer 1 is detected by a measuring apparatus 7. In addition, the polarity, magnitude and timewise characteristic thereof are analyzed and the presence or absence, magnitude and generation direction of the water tree in the cable insulator are detected to judge whether the use of the cable is succeeded.
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