Glowing contact in electrical fires: Experimental investigation and modeling on its heat intensity and thermal hazards

Abstract

Glowing contact triggered by poor electrical contacts is a typical heat source. A fire accident shows that the glowing phenomenon lasted for 8 h before flashover. Thus, it is vital to study the electrical fire risks and fire mechanisms concerning glowing contact. In this research, temperature distribution of the glowing contact is measured. A glowing contact heat transfer model is proposed based on the finite element method. Finally, experiments of thermal hazards exerted by glowing contact on insulation layers are developed. Results show that the proposed model is consistent with experimental data. It is discovered that the temperature and overheating range will increase as the oxide bridge grows. At the boundary of the oxide bridge and unoxidized wires, a turn point temperature exists. It is attributed by the low heat conductivity of the copper oxide and the good thermal conductivity of copper wires. The insulation does not catch fire but undergoes intense pyrolysis, softening, bubbling, and carbonization within a length of approximately 30 mm. According to the fire case, it can be inferred that the bared copper conductors or carbonized insulations caused by glowing contact can trigger physical short or arc short prior to electrical fires.