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 <inline-formula> <tex-math notation="LaTeX">$\text {tan}\,\delta $ </tex-math></inline-formula> for long-length submarine cables. The effect of the current limiting resistor on <inline-formula> <tex-math notation="LaTeX">$\text {tan}\,\delta $ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$\text {tan}\,\delta $ </tex-math></inline-formula> 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.