INSULATION DETERIORATED REGION EVALUATION METHOD OF CV CABLE

PROBLEM TO BE SOLVED: To evaluate a water tree generating region by grasping quantitatively a region range having much water quantity indispensable for generation of water tree, in order to solve a problem that a submerged region of a CV cable or possibility of water tree generation is estimated by a surrounding environment state hitherto, which is not quantitative evaluation. SOLUTION: A pulsed voltage is inputted from one end of a cable and its reflected wave is measured, and a cable insulator submerged region is specified from the time difference between an incident wave and the reflected wave. When a peak voltage value of the reflected wave is a prescribed value, a water tree generating region is specified.