Space Charge and Electric Field Characteristics in XLPE-Insulated Extrusion Molded Joint for HVDC Submarine Cables: Experiment and Simulation

This paper focuses on the space charge and electric field characteristics in the extrusion molded joint (EMJ) for ±500 kV HVDC submarine cables. The double-layered XLPE samples are prepared to imitate the insulation interface in the EMJ, and the space charge characteristics are assessed utilizing the pulsed electro-acoustic (PEA) method. Then, a two-dimensional simulation model for space charge based on a modified BCT model containing the ionic charges is established. The results demonstrate that the simulation outcomes based on the modified BCT model exhibit consistency with the experimental observations by measuring the mobilities and trap characteristics of electrons and holes. The results of full-sized EMJ simulation present that the negative space charges mainly accumulate near the interface, resulting in the distortion of the field in the cable insulation. Meanwhile, the interface charges diminish the electric field value at the interface but intensify the angle and tangential component of the interface field. The electric field distortion is mitigated when the crosslinking temperature for the reinforcing insulation is adjusted to 180°C. The simulation method of space charge and electric field in the EMJ insulation based on the modified BCT model can provide research means for the design and manufacture of the EMJ for HVDC submarine cables.