Effect of Different Crosslinking Agents on the DC Electrical Performance of Crosslinked Polyethylene Insulating Materials for HVDC Cables

Crosslinked polyethylene (XLPE) used in HVDC cables is typically produced through peroxide crosslinking of low-density polyethylene, and the choice of crosslinking agents significantly impacts the structures and properties of the insulating materials. Investigating the influence of different crosslinking agents on the DC performance of XLPE is valuable for the cable insulation formulation design. In this work, two typical peroxides, dicumyl peroxide (DCP) and 2,5-dimethyl-2,5-di(tert-butylperoxy) hexane (DBPH) were chosen to prepare XLPE samples. The structures of the samples were characterized by differential scanning calorimetry and the DC electrical properties were comprehensively analyzed. The results show that compared to XLPE-DCP, XLPE-DBPH exhibits a slightly lower melting temperature, improved space charge characteristics and a higher activation energy for conductivity. The differences in electrical performance between two XLPE samples can be attributed to the distinct molecular structures of two crosslinking agents. Under the same mass fraction, DBPH generates more free radicals, resulting in a higher crosslinking density, which in turn inhibits the injection and accumulation of space charge and increases the activation energy for conductivity. This investigation indicates that both XLPEs possess favorable DC electrical performance, and crosslinking agents containing two peroxy bonds per molecule also show potential for application in HVDC cable insulation.