High-voltage frequency domain spectroscopy analysis of a thermally aged XLPE submarine cable under continuous and cyclic voltage based on carrier transport and polarisation characteristics

In order to ensure the safe operation of submarine cables, it is of great significance to analyse the insulation state of submarine cables from the perspectives of microstructure, carrier transport characteristics and macroscopic dielectric properties. In this study, based on the high-voltage frequency domain spectroscopy (HV-FDS) measurement system, HV-FDS experiments of fresh and thermally aged submarine cables were carried out under continuous (0.5, 2, 4 and 10 kV) and cyclic (2-10-2 kV) applied alternating voltages. Then, combining the changes of the microstructure structure of cross-linked polyethylene (XLPE) insulation, the aggregate structure deterioration model of XLPE was proposed to discuss the physical mechanism of HV-FDS characteristics of submarine cables under different voltages and insulation states. Results show that the HV-FDS characteristics of submarine cables have significant voltage dependence under continuous voltage excitation. The HV-FDS of submarine cables show memory characteristics under cyclic voltage excitation. Compared with the fresh submarine cable, the thermally aged submarine cable shows more significant voltage dependence and memory characteristics of HV-FDS. The memory characteristics of HV-FDS are mainly determined by the carriers transport and the interfacial polarisation caused by the accumulation of polar particles at the electrode/dielectric interface. This study covers the correlation mechanism among the microstructure, carrier transport and macroscopic HV-FDS properties of submarine cable insulation, which lays a foundation for further research and condition evaluation of submarine cables.