ZR-BV单芯铜线过电流熔断痕迹形成过程

模拟聚氯乙烯绝缘阻燃(ZR-BV)单芯铜线在不同电流值时的过电流故障,借助高速摄像、视频截帧等技术,研究导线的发热过程及熔断痕迹形成过程。研究表明:导线发生过电流故障时,I≤3.5Ie,过电流导线仅出现线芯发热,绝缘热解破坏;I≥4Ie,过电流导线会发生熔断,引起绝缘层的燃烧。燃烧发生时,I<4.5Ie,导线绝缘层的燃烧仅能从熔断点蔓延至其两侧一定位置处;I≥4.5Ie,导线绝缘层的燃烧会从导线熔断点处向两侧持续蔓延,直至导线端部。导线的绝缘燃烧是结疤熔痕形成的必要条件,枝晶偏析组织是该熔痕的典型组织。在发生较大电流过电流故障时,导线会出现明火燃烧的现象。

Melted mark formation of the ZR-BV single-core copper wire under overcurrent

A simulation was conducted to study the heating process and the melted mark formation of the ZR-BV single-core copper wire under overcurrent. The formation process was shot by a high-speed camera and analyzed frame by frame. The result shows that,when overcurrent fault occurs, when I≤3.5Ie, overcurrent conductors only have the phenomenon of core heating and insulation pyrolysis damage; When I≥4Ie, the overcurrent wire will ignite the insulation.There are two kinds of insulation combustion: When I<4.5Ie, the fire of the insulation burning can spread only from the breaking point to a certain point on both sides of the conductor; When I≥4.5Ie, the fire of the insulation burning can spread to the end of the wire from the breaking point on both sides and it is this insulation combustion that causes the formation of globules. Dendritic crystal structure is the typical structure of globules. This study shows that there will be flame when energized conductor carries large current.