Space Charge and Electric Field Distributions in Extrusion Molded Joint for ±500 kV HVDC Cables

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. Under polarity reversal voltage, the electric field at the interface increases abruptly to 39.5 kV/mm.