Study on Metallographic Structure of Melted Breakpoint mark for Copper Wire Current Overloading

Abstract

As a common electrical fault causing fire, current overload results in some trace evidences on the wire. However, most of relative evidences, such as insulating layer, metal core, are likely to be destroyed or disturbed by fire. The majority of wire evidences from fire are asked to test melted breakpoints marks of the wire. Thus, it is significant to clearly reveal the metallographic features of melted breakpoint mark for wire overloading for fire investigators. This paper selected two kinds, single-core and multi-cores, 1.5mm2 copper wires to make melted breakpoints with 100A current overload. Then, this paper did some research on the fire heat influence on the microstructure of melted breakpoints. Experimental results indicated that the metallographic structure of the melted breakpoint mark caused by current overload was significantly different from that of melted mark caused by fire and short circuited melted mark. As for melted breakpoint marks of copper wire overloading, the most distinctive feature of the metallographic structure was dendritic segregations existing.