Numerical-statistical analysis of void-induced electric field intensification in XLPE insulation for HVDC cables

Voids within cables insulated with XLPE are inevitable micro-defects that critically threaten HVDC cable reliability by local electric field (E-field) intensification. A multi-factor (MF) approach is essential for enabling a comprehensive quantitative assessment that simultaneously considers the combined effects of these parameters. This study aimed to analyze the E-field intensification in void-containing XLPE-insulated HVDC cables. Hybrid numerical-statistical approach was applied to investigate the effects of critical void parameters — aspect ratio, location, void count, and relative permittivity — using finite element method (FEM) simulations integrated with central composite design (CCD)-based response surface methodology (RSM). A strong correlation was observed between the simulation results and model predictions (R2 > 0.97). The derived predictive model identifies a single air-filled void, shaped like an oblate spheroid with a small aspect ratio and located near the conductor, as the most dangerous defect, amplifying E-field to approximately 35.11 kV/mm. Analysis of variance revealed that the void location was the most dominant factor affecting the maximum E-field (41.91%). A critical, non-linear interaction was found between the aspect ratio and the relative permittivity of voids (15.21%). This work provides a tool for defect severity ranking and proposes engineering tolerances to mitigate breakdown risk from manufacturing defects.