A novel method for uniform electric field distribution in HVDC cables

Temperature grading within the cross-linked polyethylene (XLPE) insulation presents a significant challenge for extruded cables due to the high dependence of electrical resistivity on temperature, which can cause electric field distortion in High-voltage direct current (HVDC) cables. This paper proposes a novel method to enhance the electric field uniformity by incorporating BaTiO
3
-based ceramic fillers with positive temperature coefficient (PTC) electrical resistivity into XLPE. Curie temperature of $60^{\circ} \mathrm{C}$ PTC material (BT60) is selected, the melt blending process is used to prepare XLPE/PTC composites with different doping content, and the corresponding physicochemical and mechanical properties are characterized. The temperature dependence of the electrical resistivity of the XLPE/PTC composites decreases with increasing addition content, and BT60-10 shows the lowest activation energy of 0.63 eV, which is 31.5% lower than the activation energy of 0.92 eV for XLPE. The electric field distortion value of the cable is consistent with the trend of the Arrhenius activation energy. Reducing the electrical resistivity activation energy of the XLPE/PTC composite insulating material enables a maximum lowering of the electric field inside the cable insulation, resulting in a more homogeneous electric field distribution. BT60-10 significantly reduces the electric field distortion of the cable insulation layer by 42.5%. The results of this study could contribute to the research and development of high-performance insulating materials for HVDC cables.