In order to accurately assess the insulation of cross-linked polyethylene（XLPE） cables in power distribution networks

we researched non-destructive detection devices and relevant assessment methods based on the characteristic parameters of polarization-depolarization current（PDC）. Taking new and aged cables with different lengths for examples

we analyzed and compared their insulation using the PDC method. By comparing the depolarization discharge current curves of cables

it is found the current level plunges from μA to n A at the beginning of the discharge

meanwhile

the aged cables discharge faster than their newer counterparts. Then after a certain while

the current level falls from n A to p A and eventually stabilizes at p A level

at this time the depolarization current of aged cables is much larger than that of the new cables. Depolarization current increases with the charging voltage and the charging time. In the end

through non-linear fitting of the experimental data

we can obtain the relationship between the fitted curves and the dielectric constant and conductivity of the cable insulation layer. The results verify the accuracy and reliability of the PDC method in assessing XLPE cable insulation.