Influence of semiconductive shielding protrusions on the electric field distribution in ±500 kV HVDC cables

High-voltage direct current (HVDC) cables demand a high-performance insulation system to ensure the operational reliability. Protrusions located on cable interfaces can cause electric field distortion, resulting in insulation degradation and a reduced lifespan. By using the finite element method, a 3D model was established to explore how protrusions affect the electric field within HVDC cable insulation, considering different sizes and shapes of protrusions, the activation energy of conductivity for insulation materials and the temperature difference across the insulation. The results indicate that under full load conditions, protrusions at the interface between the insulation layer and the semiconductive shielding layer significantly affect the electric field distribution, and the height of the protrusion has a greater impact than the cross-sectional shape and size. By increasing the protrusion height from 50 μm to 300 μm, an increase of electric field distortion rate from 9.78 to 102.04 was observed. Furthermore, the electric field distortion rate near the protrusions exhibits a positive correlation with the activation energy of the insulation material, specifically increasing by 0.72 for every 0.1 eV increment. These findings provide valuable insights for the design and evaluation of HVDC cable insulation.