| 摘要 |
PURPOSE:To eliminate influences of local batteries existing at locations where the insulation of the main body of a power cable and the shielding material are inferior so as to obtain an accurate measured result by finding the insulation inferior resistance value of the main body and shielding material through arithmetic. CONSTITUTION:The value of a DC voltage EO generated in a shielding material 8 is measured with a DC voltmeter 13' with a switch 5 being opened and a change-over switch 16' at a cable 6 side to be measured being set to a change-over position (II'). Then the switch 5 is closed and the voltage value E of a DC for measurement from a measuring DC source 4 is superimposed on a high tension bus 1 while the switch 16' is maintained at the change-over position (II'). A voltage value E1 obtained with the voltmeter 13' under this condition is inverted in polarity as compared with the voltage value EO and the shielding material 8 side becomes negative. After the voltage value E1 is obtained, the switch 16' is switched to another change-over position (III') and a voltage value E2 indicated by the voltmeter 13' is read. The insulation inferior resistance value of the main body and shielding body of the cable to be measured are found through arithmetic based on these three measured voltage values EO, E1, and E2.
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