Polarization and depolarization current measurement applied for investigation of underground cable system problems

This research investigates the problems in XLPE cables system. The 12/20(24) kV underground cable with the cross section area of 240 mm² was used in the experiment. Two 3 meter long cables were connected by a cable joint where the defect was simulated on. The dielectric investigation of XLPE cable system by polarization and depolarization current (PDC) measurement was performed comparatively among four different cases: a healthy cable with healthy heat shrinkable joint (case1), a cable joint with an incision on XLPE surface (case2), a cable joint contaminated with 20 micron iron powder on XLPE surface (case3) and a cable joint contaminated with 20 micron copper powder on XLPE surface (case4). Diagnostic parameters, PDC shapes, dielectric dissipation factor (DDF) and conduction current, derived from PDC test results for analyzing the dielectric response are proposed in this paper.