| 摘要 |
PROBLEM TO BE SOLVED: To improve workability of insulation deterioration diagnosis of a cable by canceling a reactive charge signal independent of application of alternating voltage, in the case that the water tree insulation deterioration diagnosis of existing power cables by a residual charge method and clearly displaying forced residual charge by the application of the alternating voltage. SOLUTION: After the insulation layer of a cable to be diagnosed is charged, a cable conductor is earthed once, change of the residual charge of the cable is changed over from an earthed stage to a stage detected by a detection capacity Cd , the alternating voltage Vac is applied in order to accelerate discharge of the residual charge in the detection stage, and the insulation deterioration of the cable is diagnosed from the detection result in the detection stage. A detection signal is canceled by a cancelling voltage source Vx during non- application of the alternating voltage. |
