How to improve the insulation performance of XLPE cable material?
Release Time : 2025-11-17
XLPE cable material, with its excellent insulation properties, has become a core material in the medium- and high-voltage power transmission field. Its performance optimization requires a comprehensive approach from multiple dimensions, including material molecular structure, process control, interface design, and environmental adaptability, forming a repeatable and traceable improvement system.
The improvement of XLPE's insulation performance begins with precise control at the molecular level. Through chemical cross-linking, the polyethylene molecular chain transforms from a linear structure to a three-dimensional network structure, significantly enhancing the material's thermal stability and electrical breakdown strength. The uniformity of cross-linking is a key indicator; insufficient local cross-linking leads to a decrease in mechanical strength, while over-cross-linking may increase brittleness. In production, it is necessary to control the precursor ratio, mixing temperature and time, dehydration, and post-curing processes to ensure a more uniform distribution of the cross-linked network. For example, when using peroxide to initiate cross-linking, the extruder temperature gradient must be precisely controlled to avoid the formation of coke particles at the flange due to excessive temperature, while nitrogen protection reduces oxidation byproducts, thereby improving insulation purity.
The impact of interface design on insulation performance is also significant. XLPE cables typically employ a three-layer co-extrusion structure. The interface matching between the conductor shield, insulation layer, and semiconductor shield directly affects the electric field distribution. If micropores or protrusions exist between the insulation and shield layers, electric field distortion will accelerate localized aging. By optimizing the die design and employing a combined extrusion die, the three layers can be extruded densely and uniformly, resulting in a smooth interface. Furthermore, introducing nanoscale inorganic fillers, such as nano-SiO₂ or Al₂O₃, into the insulation layer can suppress space charge accumulation and reduce polarization damage. These fillers, through dispersion optimization, can improve thermal stability and reduce electric field concentration, thereby extending insulation life.
Environmental adaptability is another key focus of XLPE insulation performance optimization. Humid environments can lead to the formation of "water trees" within the insulation layer, significantly reducing dielectric strength. To inhibit moisture intrusion, both material modification and structural protection are necessary. On the one hand, the hygroscopicity of the material is improved by filling it with water-blocking fillers such as micro-nano-sized aluminum hydroxide. On the other hand, high-barrier sheath materials, such as thermoplastic polyurethane (TPU), are used, and the cable end sealing process is optimized to prevent moisture from penetrating from the ends or damaged sheaths. For high-temperature and high-humidity environments, hydrophobic modifiers can also be introduced to reduce the surface energy of the insulation layer and reduce moisture adhesion.
Process control is the core link in ensuring the stable performance of XLPE insulation. During production, defects such as impurities, micropores, and protrusions must be strictly monitored. Impurities mainly originate from insufficient purity of raw materials or contamination during processing, and must be controlled through ultra-clean cross-linkable polyethylene insulation materials and a closed production environment. Micropores are closely related to the degassing efficiency of cross-linking byproducts; using efficient degassing processes, such as vacuum drying and inert gas protection, can significantly reduce the content of residual byproducts. In addition, online detection technologies, such as silicone oil testing, can be used to observe the pores and protrusions inside the insulation layer in real time to ensure product quality.
Performance maintenance during long-term operation is equally crucial. XLPE insulation gradually ages under the combined effects of electric fields, heat, and mechanical stress, requiring regular testing and assessment of its health status. Technologies such as polarization-depolarization current testing and space charge distribution measurement can quantify the impact of polarization processes on long-term stability. For aging cables, local repair techniques, such as injecting restorative insulation materials, can be used to restore their insulation performance. Simultaneously, establishing an on-site online monitoring system, combining temperature, insulation resistance, and partial discharge signals, allows for health grading and remaining life assessment, providing a scientific basis for operation and maintenance.
In the future, the optimization of XLPE cable material insulation performance will focus more on environmental friendliness and adaptability to extreme conditions. This includes developing halogen-free flame-retardant modified materials to reduce toxic gas emissions during combustion; and improving the material's radiation resistance and corrosion resistance for extreme environments such as marine and mining areas. Furthermore, interdisciplinary collaborative innovation, such as the combination of nanomaterial modification, interface engineering, and digital manufacturing, will provide new pathways to improve the overall reliability and economy of cable systems.