A Novel PDC System and tan δ Calculation Process for Insulation Diagnosis of Submarine Cables

This article presents a novel polarization and depolarization current (PDC) system and calculation process of
$\text {tan}\,\delta $
for long-length submarine cables. The effect of the current limiting resistor on
$\text {tan}\,\delta $
was analyzed by the Debye model and found to be significant as the cable length increases. To eliminate this effect, a revised process was proposed for making the PDC method suitable for the insulation diagnosis of high-voltage (HV) submarine cables. Simulation results revealed that a sampling interval of 0.04 s is appropriate for
$\text {tan}\,\delta $
calculation at 0.1 Hz. We also adjusted the picoammeter to the HV side compared with the traditional PDC test system. Finally, we carried out PDC tests on four in-service cables, which clearly show their insulation condition and verify the validity of the PDC method for insulation diagnosis of HV submarine cables.