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.