Characteristics of Charge Accumulation at the Interface of Double-Layer XLPE Under DC Voltage

The factory joint is a critical component within high-voltage direct current (HVdc) submarine cable transmission systems, profoundly impacting the stability of equipment operation through its insulation interface performance. However, the characteristics of space charge accumulation at the interface of double-layer cross-linked polyethylene (XLPE) insulation in factory joints, arising from variations in the fabrication process, remain largely unexplored. Therefore, this article investigates the effects of the degree of cross-linking and contact tightness on space charge accumulation characteristics within the double-layer XLPE interface. Experimental findings indicate that the degree of cross-linking alters the carrier mobility of XLPE and the polarity of charges accumulated at the interface of the double-layer sample. In addition, the contact tightness of the double-layer sample can affect the amount of charges accumulated at the interface. Then, based on the simplified bipolar carrier transport model, the key parameters of the simulation are optimized using the particle swarm optimization (PSO) algorithm, and the values of the interface barriers are obtained. Finally, the behavior of interface charge accumulation is successfully explained in terms of the differences in the mobilities and the interface barriers for positive and negative charges. This study offers valuable guidance for the utilization and maintenance of HVdc cable factory joints.