Simulation Study on the Extrusion Performances Based on the Viscosity Parameters of Cross-Linked Polyethylene Insulating Materials for High-Voltage Cables
Shang Kai, Li Jiacai, Wang Shihang, Li Shengtao
State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University Xi’an 710049 China
Abstract：The cross-linked polyethylene (XLPE) insulating materials and its extrusion molding technology for high-voltage cables are key issues for the production of high-voltage cables in China. The insulating materials are composed of low-density polyethylene (LDPE) by introducing cross-linking agent (dicumyl peroxide (DCP)) and antioxidants. The extrusion molding of XLPE insulation for high-voltage cables is a process in which the XLPE melt is continuously triple extruded and coated with metal conductors, and then undergoes cross-linking reaction to form high-voltage cable insulation. The viscosity parameters of the insulating materials melt will affect its extrusion performances in the single-screw extruder, such as the flow rate of the extrusion outlet and the maximum temperature of the melt in the flow channel, which in turn determine the molding quality and insulation properties of the cable insulation. This paper discussed the influence of the viscosity parameters of the high-voltage cable XLPE insulating materials on extrusion performances by means of simulation, and proposed to use the maximum temperature-extrusion outlet flow rate curve during insulating materials extrusion process to reflect the change rule of extrusion performances under different viscosity characteristics. The results show that the maximum temperature increases with the increase of the flow rate at the extrusion port, the zero-shear viscosity and relaxation time have the greatest influence on the slope of the maximum temperature-extrusion port flow rate curve, followed by the power law index, and the temperature coefficient has the least effect. Among them, the zero-shear viscosity and power law index are positively correlated with the flow rate at the extrusion port and the maximum temperature, and the flow rate at the extrusion outlet does not increase significantly after the zero-shear viscosity increases to a certain value, but the maximum temperature continues to increase. Meanwhile, the relationship between relaxation time and temperature coefficient is negatively correlated with the flow rate of the extrusion port and the maximum temperature, and the smaller the temperature coefficient is, the better the extrusion performances are. Finally, according to the actual extrusion production requirements of cable insulation material, the optimum range of viscosity characteristic parameters of insulation material is determined. Therefore, in terms of improving domestic insulation materials, the first priority is improving the relative average molecular weight of the LDPE base material in the insulation materials, followed by optimizing the molecular weight distribution and appropriately increasing the number of long chain branches to adjust the viscosity parameters of the high-voltage cable cross-linked polyethylene insulation materials, which can improve its extrusion properties. This study can provide important data support and theoretical basis for the development of domestic high-voltage cable cross-linked polyethylene insulation materials and the improvement of extrusion molding technology. Based on this research, the improvement strategy of great extrusion performances in high-voltage cable insulating materials will be explored in the future from the perspective of regulating the molecular chain structure of LDPE.
尚恺, 李加才, 王诗航, 李盛涛. 高压电缆交联聚乙烯绝缘料黏度参数对挤出特性影响的仿真研究[J]. 电工技术学报, 2024, 39(3): 810-819.
Shang Kai, Li Jiacai, Wang Shihang, Li Shengtao. Simulation Study on the Extrusion Performances Based on the Viscosity Parameters of Cross-Linked Polyethylene Insulating Materials for High-Voltage Cables. Transactions of China Electrotechnical Society, 2024, 39(3): 810-819.
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