Improved DC Conductivity and Space Charge Characteristics of XLPE for HVDC Cable Application: Effect of Voltage Stabilizers

Electric field distortion caused by the DC conductivity variation and space charge accumulation under temperature gradient in the cross-linked polyethylene (XLPE) insulation is the most serious problem in HVDC cable application. In this paper, three different voltage stabilizers, Bis(4-fluorophenyl)-methanon, Bis(4-hydroxyphenyl) ketone, and Bis[4-(dimethylamino)phenyl] diketone, denoted as A, B, and C, respectively, were mechanically dispersed into the XLPE material with an addition of 0.5 wt%, aiming at improving the DC conductivity characteristics and space charge behaviors of the XLPE insulation at different temperature. The DC conductivity under different temperature and the electric field was tested by a three-electrode system. Meanwhile, space charge properties at 30 °C and 90 °C were investigated using PEA method, and the trap level distribution was estimated by the surface potential decay (SPD) process. The experimental results indicate that all the three voltage stabilizers have improved the DC conductivity characteristics of the XLPE, especially the voltage stabilizers B and C. In addition, the XLPEs modified by the voltage-stabilizers B and C with higher deep trap level demonstrate an excellent ability on space charge suppression at different temperatures. It is concluded that owing to the excellent voltage stabilizing effect, the voltage stabilizers B and C show much potential in HVDC cable application.