Interface Charge Characteristics of Double-Layer Laminated XLPE Samples for HVDC Cable Factory Joint

Under direct-current (DC) electric fields, space charge distribution will form at the insulation interface of the factory joint, causing electric field distortion and may lead to insulation breakdown. In this paper, the double-layer laminated XLPE samples and cable insulation/restoration insulation samples were prepared according to the manufacturing process of factory joints respectively and the space charge distribution, charge trap properties and crystallization properties were investigated. For completely degassed double-layer laminated XLPE samples, interface charge peaks with opposite polarities to the electrodes on both sides will appear after the voltage applied for a little while, due to the inconsistent conductivity at the interface. Then with the charge injection from the electrodes on both sides, deep traps at the interface begin trap the injected charge, forming space charge accumulation of negative polarity at the interface.