Abstract
In this work, we apply a computational diffusion model based on Fick’s laws to study the generation and transport of methane (CH) during the production of a cross-linked polyethylene (XLPE) insulated cable. The model takes into account the heating process in a curing tube where most of the cross-linking reaction occurs and the subsequent two-stage cooling process, with water and air as the cooling media. For the calculation of CH generation, the model considers the effect of temperature on the cross-linking reaction selectivity. The cross-linking reaction selectivity is a measure of the preference of cumyloxy to proceed either with a hydrogen abstraction reaction, which produces cumyl alcohol, or with a -scission reaction, which produces acetophenone and CH. The simulation results show that, during cable production, a significant amount of CH is generated in the XLPE layer, which diffuses out of the cable and into the conductor part of the cable. Therefore, the diffusion pattern becomes a non-uniform radial distribution of CH at the cable take-up point, which corresponds well with existing experimental data. Using the model, we perform a series of parametric studies to determine the effect of the cable production conditions, such as the curing temperature, line speed, and cooling water flow rate, on CH generation and transport during cable production. The results show that the curing temperature has the largest impact on the amount of CH generated and its distribution within the cable. We found that under similar curing and cooling conditions, varying the line speed induces a notable effect on the CH transport within the cable, while the cooling water flow rate had no significant impact.
Highlights
Cross-linked polyethylene (XLPE) is one of the most commonly used materials for power cable insulation because of its relatively low cost, simple processability, excellent electrical properties, and its resistance to chemicals and moisture [1]
The heat generated from the cross-linking reaction, 900 kJ·kg−1 of Dicumyl peroxide (DCP) is negligible compared to the amount of energy supplied by the curing tube [19,20]
Our results showed that the CH4 generation in the cable was significantly influenced by the reaction selectivity
Summary
Cross-linked polyethylene (XLPE) is one of the most commonly used materials for power cable insulation because of its relatively low cost, simple processability, excellent electrical properties, and its resistance to chemicals and moisture [1]. The cable is placed in a degassing chamber and the chamber temperature is typically controlled to around 70 °C to facilitate byproduct removal from the power cable This process is expensive and time consuming, and is considered to be a critical bottleneck for cable production, especially for HV and EHV power cables, which generally have thicker insulation [3]. The objective of this study is to apply a computational diffusion model with various in-situ cable manufacturing conditions and study the transport of the byproducts that are generated by the PE cross-linking reaction during cable production, before the cables are degassed. This model can be applied using different diffusion-related parameters to consider the transport of other byproducts such as acetophenone (AP) and cumylalcohol (CA) Using this model, we perform several parametric studies to numerically determine and characterize the critical cable production parameters that affect CH4 generation and transport processes during cable extraction and production
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