The Influence of Currents on the Ignition and Correlative Smoke Productions for PVC-Insulated Electrical Wires

Ignition of energized polyvinyl chloride insulated copper conductor wires by external heating was investigated for a better understanding of the initiation of electrical wire fires. First, a simplified theoretical analysis was developed to quantitatively explain the effects of currents on the ignition of electrical wires. The numerical result predicted that the ignition time concavely decreases with the increasing external heat flux while convexly decreasing with the increasing current of wire. Second, experiments with several sample wires were conducted to study the ignition process. It showed a good consistency between the experimental and numerical results. Using the methods of Transmission Electron Microscope, Scanning Electron Microscope and Fast Particulate Spectrometer, the properties of released smoke productions were obtained. The smoke particles size distribution was found independent to the current of wire and showed the same morphology with the standard test fires. The properties of pyrolysis smoke particles showed a two-regime behavior with the increasing current of wire. The pyrolysis smoke particle size distribution with one certain current showed a bimodal phenomenon. The three-stage changes of the count median diameter and geometry mean diameter were also presented.