An experimental study on the combustion process and thermodynamic characteristic parameters of copper wire overcurrent fault

The overcurrent fault of copper wire is an important cause of electrical fire, and the combustion process of which is relatively complicated. In this study, the rated current of 32A of the wire was taken, and the electrical fault simulation device was used. After the overcurrent I_o was set to 128A, 160A, 192A, and 224A, respectively, to analyze the combustion evolution process of PVC-insulated copper wire, the evolution of pyrolysis gas from the insulating layer, and the change of functional groups. The results show that when the overcurrent fault of PVC-insulated copper wire happened, the core wire was turning red, the wire was deforming, the smoke was releasing, the insulating layer was dripping, the wire was fusing, and the continuous burning occurred. When the current I_o < 160A, there was only one fusing point on the wire. In addition, when an overcurrent fault occurred in the PVC-insulated copper wire, the temperature rise rate increased exponentially, which can be divided into three stages of the initial heat accumulation stage, the wire fusing stage, and the continuous burning stage. Furthermore, CO, HCl, CH₄, olefins, and aliphatic and aromatic compounds were precipitated during the combustion process of the PVC insulating layer. The quality of the insulating layer decreased with the increase in temperature, and the weight loss rate was higher at 300°C. The conclusions of this study have provided experimental basis and technical support for the physical and evidence identification of fire accidents.