Polarization-depolarization Current Method for XLPE Cable Insulation Diagnosis

XLPE cable is now widely used in distribution network, and its insulation diagnosis is related to power grid reliability. Polarization and depolarization current (PDC) method is applied to evaluate degradation status of various aging overhead insulated lines. The experimental samples are originated from actual operation cables and laboratory accelerated aging cables, characterized by different operation time. In this paper, voltage resistance tests of actual cables indicate influences of aging on insulation degeneration. And XLPE samples are accelerated of 80℃ thermal aging, and then measured by PDC test at constant temperature condition. The obtained results indicate that with increasing of aging time, the impurities show that impurities polarization dominates the depolarization current, and characteristic parameter of aging factor is growing from good to critical. Peak-differenating analysis confirms the evolution of aging trend, and functions as a temporal variation law. The verification results prove that PDC method is an effective and rapid access of degradation status assessment.