INSULATION DETERIORATION DIAGNOSIS METHOD AND INSULATION DETERIORATION DIAGNOSIS DEVICE OF POWER CABLE

摘要

PROBLEM TO BE SOLVED: To provide an insulation deterioration diagnosis method and an insulation deterioration diagnosis device which are capable of diagnosing a state of a part where insulation deterioration of a power cable due to a water tree is worst, without depending on a length of the power cable.SOLUTION: The insulation deterioration diagnosis method comprises: a measurement step of measuring an impressed voltage of an AC voltage as a second impressed voltage and an amount of residual charge emitted by voltage impression, in parallel; an increment measurement step of measuring an increment of residual charge due to boost of the AC voltage on the basis of residual charge at the time of the start of AC voltage impression; a rise time measurement step of measuring a rise time when the increment of residual charge reaches a prescribed value; an AC voltage value measurement step of measuring an AC voltage value of the AC voltage being impressed at the rise time; a rise electric field calculation step of calculating an AC electric field at the time when the increment of residual charge reaches the prescribed value, as a rise electric field on the basis of the measured AC voltage value; and a diagnosis step of diagnosing a state of a part where insulation deterioration of the power cable is worst, on the basis of the calculated rise electric field.