Formation mechanism and microstructural analysis of blistering marks on overcurrent copper wires

Abstract

Electrical fires frequently result in severe casualties, with overcurrent faults being a primary cause. This study investigates the formation mechanisms of blistering marks on polyvinyl chloride (PVC) insulated copper wires, traditionally attributed to direct flame exposure. We conducted a comprehensive analysis of PVC copper wires subjected to overcurrents ranging from 190 to 240A, examining the resultant microstructural changes. Our findings challenge conventional beliefs by demonstrating that certain blistering marks, especially on non-flame-retardant PVC (NF-PVC) insulated wires, are indicative of overcurrent faults rather than flame exposure. By integrating detailed microstructural analysis with the thermal decomposition characteristics of the PVC insulation, this study provides new insights into diagnosing the causes of electrical fires and advocates for more meticulous methods in fire investigations.