| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and an apparatus wherein the insulation degradation of one each for each phase, a total of three CV cables 1, 1, is diagnosed collectively with reference to a commercial three-phase AC voltage, when their insulation is degraded, to which extent any of the CV cables 1 is degraded can be specified and the insulation degradation can be diagnosed easily, precisely and at low costs. SOLUTION: While the respective CV cables 1, 1 are set to a hot-line state, AC voltages at respective phases constituting a low-frequency three-phase AC voltage for diagnosis are applied to shielding layers constituting the respective CV cables 1, 1 by a three-phase power supply 8 for diagnosis. In this state, a current flowing in a grounding conductor 7 which collectively grounds the shielding layers is measured by a measuring device 9. From among current components contained in the current measured by the measuring device 9, a current component whose frequency is identical to that of the three-phase AC voltage for diagnosis is observed. Thereby, the insulation degradation of the three CV cables 1, 1 is diagnosed.
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