Measurement of Electrical Properties and Polarity-Reversal-Induced Space Charge Dynamics in 500-kV EHVDC Cable Factory Joints Under Different Vulcanization Times

Vulcanization time is crucial for the insulation performance of 500 kV extra high voltage direct current (EHVDC) submarine cable factory joints. In this study, transition layer specimens with varying vulcanization times were prepared to simulate the interface of the factory joint. The electrical properties and microstructure of the specimens were analyzed. A bipolar charge transport simulation model of the factory joint under polarity-reversal voltage was established. The results demonstrate that extending the vulcanization time promotes interfacial merging of the transition layer and introduces micro-voids at the interface. At a vulcanization time of 90 min, enhanced interfacial fusion effectively suppresses space charge accumulation, leading to improved electrical performance at elevated temperatures. For full-sized factory joints, elevated temperatures enhance carrier mobility and accelerate charge redistribution during polarity reversal. As a result, space charge accumulation becomes increasingly governed by interfacial properties, leading to pronounced polarity-dependent charge behavior at the transition interface. This study provides a reference for optimizing vulcanization parameters of factory joints and for improving the space charge distribution within them under voltage polarity reversal.