This invention discloses a cross-linked
polyethylene insulation material for medium-
voltage DC cables and its preparation method. By weight, it comprises the following raw materials: 100-110 parts LDPE, 5-8 parts modified filler, 0.4-0.6 parts
antioxidant, 0.2-0.3 parts cross-linking aid, and 0.4-0.7 parts initiator. The modified filler, prepared by a specific method, combined with an optimized cross-linking and
antioxidant system, significantly improves the overall performance of the insulation material. This modified filler, through the synergistic effect of its deep trap energy levels in the core and the shallow trap energy levels of the outer
organic molecules, increases the
DC resistivity and breakdown
field strength of the material. Simultaneously, the flexible long-
chain structure grafted onto the filler surface improves its interfacial compatibility with the
polyethylene matrix, giving the material excellent mechanical properties that meet the stringent requirements for long-term safe and stable operation of medium-
voltage DC cables.