A Health Indicator Sensitive to Non-uniforming Aging Patterns of Polymeric Insulation Systems

In the context of green energy transition in extra-high-voltage (EHV) power transmission, EHV polymeric cable connecting power generation and loads is a key power asset in the large-ampacity power system. However, harsh operating environments brought from renewable energy and power electronics will create a huge challenge to EHV cable insulation reliability. Notably, EHV cables with enough insulation margins has above 40 mm thicker insulation layers, which easily cause the non-uniform aging mechanism different from the uniform aging mechanisms of the low-voltage cable insulation. The nonuniform aging pattern is a more disastrous factor to trigger local partial discharges and shorten the expected cable insulation lifetime. Therefore, this paper devotes to investigating a new aging state assessment approach of polymeric insulation systems affecting by the non-uniform aging pattern, with a focus on EHV cable, based on the circuit modeling and frequency-domain broadband dielectric spectroscopy technique. Firstly, the influence difference between non-uniform aging and uniform aging on the BDS behaviors is analyzed. Then, a novel circuit model is constructed to identify the effective health indicator from the measured BDS. Finally, the assessment model between health indicators and aging states is determined. This paper will provide a solid theoretical basis for the insulation state diagnosis of EHV submarine cables.