Research on the process of short-circuit faults induced by overcurrent in copper-clad aluminum sheathed wire and the characteristics of weld marks
Copper-clad aluminum sheathed cables are commonly utilized as a cost-effective and lightweight alternative to copper-core sheathed cables.However,their lower carrying capacity renders them more vulnerable to overcurrent faults,which can induce short circuits and pose a fire hazard.This article aims to offer technical insights for comprehending and examining these fire-related incidents.This study investigates the characteristic patterns of fault occurrences,with a focus on voltage and current fluctuations during the process.It explores key process parameters such as the time to short circuit occurrence,number of arcing instances,and duration of combustion,across varying overcurrent values.Furthermore,the study identifies typical characteristics of melting marks and metallographic microstructures resulting from overcurrent-induced faults.The findings indicate that 5.50 times the rated current(denoted as Ie)represents the minimum current threshold at which overcurrent faults can induce short circuits in copper-clad aluminum sheathed cables.The time for a short circuit to occur decreases exponentially with higher overcurrent values,reducing from 148.9 s at 5.50Ie to 40.1 s at 8.80Ie.Notably,the duration of combustion after ignition of the short circuit initially increases and then decreases,with the longest duration of 22.72 s observed at 7.15Ie.Short circuits induced by overcurrent in these cables often involve multiple repeated arcing instances,with up to 55 arcs observed.The repeated arcing generates numerous wire core arc melting marks and short-circuit splattered melting beads.These marks typically manifest as bead-like or stacked bead-like shapes,often displaying dendritic crystal patterns in their internal structure.The findings of this study offer critical insights into identifying the origins of fires linked to copper-clad aluminum sheathed cables.Such understanding is essential for precise trace identification and can contribute to enhancing fire safety protocols and standards within the electrical industry.
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