| 摘要 |
PURPOSE:To exactly measure a residual voltage while eliminating the influence of a space charge and current leak at the terminal end of a cable by setting the leak time constant between a cable conductor and the ground during grounding of a guard electrode at >=100min. CONSTITUTION:The distance l0 between the top end of the guard electrode 3 wound with metallic foil or semiconductive tape on a sleeve pipe at the terminal end of the cable and an exposed part 23 on a high voltage side at the terminal end of the cable is so set that the leak resistance between the cable conductor and the ground is >=100min. when the electrode 3 is grounded together with the shielding layer on the outside of the cable. A switch SW2 is brought into contact with a contact (a) to impress a DC high voltage DC for a prescribed period to the cable conductor and the electrode 3 and thereafter a switch SW1 is closed and the switch SW2 is brought into contact with a contact (b) to ground the cable conductor and the guard electrode for the prescribed period in the stage of measurement. A switch SW3 is then closed to release the grounding of the cable conductor and the potential of the cable conductor thereafter if measured with an electrometer V while the electrode 3 is held grounded.
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