In high-voltage direct current cable systems

the factory joint of cross-linked polyethylene (XLPE)-insulated cables presents significant electrical breakdown risk. The charge accumulation mechanism at the XLPE–XLPE interface involves the accumulation of opposite charges on both sides of the interface

thereby complicating the comprehension of the interfacial charging phenomenon. This study investigates the fundamental mechanisms of charge accumulation and the associated homo-junction effect in homo-bilayer XLPE (H-XLPE). Space charge analysis

model calculations based on Maxwell's equations

and thermal stimulation depolarisation current (TSDC) measurements were performed. Space charge results show that the homo-junction-induced charge accumulation causes greater electric field distortion

leading to lower breakdown strength of H-XLPE compared to single-layer XLPE. Model calculations indicate that the density of opposite charges on the interface is attributed to the local gradient of reciprocal conductivity in the H-XLPE interface region. TSDC measurements on XLPE and H-XLPE enabled extraction of trap parameters and analysis of the charge transport process. The findings provide experimental evidence and theoretical clue for elucidating the role of the interface area on the charge accumulation that affects reliability and stability of submarine cable systems.