| 摘要 |
PURPOSE:To make it possible to more accurately judge the insulation deteriorated state of a power cable, by superposing low frequency AC voltage to a cable in a hot-line state while measuring an AC leak current corresponding to a DC leak current component. CONSTITUTION:Low frequency signal voltage is injected from the neutral point of an earthing transformer 7 connected to a bus 8. The earthing wire of the transformer 7 is opened in measurement and a signal is inputted from a low frequency power source 3. At this time, one of the earthing wires of a cable 9 to be measured is earthed through impedance 1 from current detection and the voltages at both terminals of the impedance are measured by a signal detecting apparatus 4. In addition, the detecting apparatus 4 is formed of a band filter, an amplifier, a data processing part, a recording part and a data output part.
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