Study of Partial Discharge Characteristics in Medium Voltage Cable Insulation with Internal Defect

Inception of partial discharge (PD) is an important indicator of insulation degradation in power system assets, including cables. The characteristics of PD activity measured during ongoing degradation process provide information regarding the nature and severity of insulation defects. This study investigates the behavior of PD in a medium voltage (MV) cable sample with an artificial defect developed by making a cut on the outer jacket towards the shielding that extends into the main insulation. The PD activity is measured using a high frequency current transformer. A number of PD characteristics: peak pulse height, phase of occurrence, and pulse repetition rate are extracted from the PD measurements using a local maxima-based algorithm. The behavior of the PD activity based on these characteristics is analyzed under increasing electrical stress. This study can be useful in analyzing the aging and degradation behavior of solid insulating materials.