Numerical Analysis of a Continuous Vulcanization Line to Enhance CH₄ Reduction in XLPE-Insulated Cables

Herein, we apply a computational diffusion model based on Fick’s law to study the manner in which a cable production line and its operating conditions can be enhanced to effectively reduce the CH${}_4$ concentration in cables insulated with cross-linked polyethylene (XLPE). Thus, we quantitatively analyze the effect of the conductor temperature, curing tube temperature distribution, transition zone length, and online relaxation on CH${}_4$ generation and transport during the production of 132 kV cables with an insulation thickness of 16.3 mm. Results show that the conductor temperature, which is initially controlled by a preheater, and the curing tube temperature distribution considerably affect the CH${}_4$ concentration in the cable because of their direct impact on the insulation temperature. The simulation results show 2.7% less CH${}_4$ remaining in the cable when the preheater is set at 160 °C compared with that when no preheater is used. To study the curing tube temperature distribution, we consider three distribution patterns across the curing tube: constant temperature and linear incremental and decremental temperature. The amount of CH${}_4$ remaining in the cable when the temperature was linearly increased from 300 to 400 °C was 1.6% and 3.7% lower than in the cases with a constant temperature at 350 °C and a linear temperature decrease from 400 to 300 °C, respectively. In addition, simulations demonstrate that the amount of CH${}_4$ removal from the cable can be increased up to 9.7% by applying an elongated and insulated transition zone, which extends the residence time for CH${}_4$ removal and decelerates the decrease in cable temperature. Finally, simulations show that the addition of the online relaxation section can reduce the CH${}_4$ concentration in the cable because the high cable temperature in this section facilitates CH${}_4$ removal up to 2.2%, and this effect becomes greater at low production speeds. View Full-Text