Comparative analysis of overload ignition of electrical wires under varying test conditions

The ignition behavior of electrical wires induced by overload current can be significantly impacted by even minor experimental alterations. However, there is currently no standardized testing procedure. This work investigated the effect of test conditions (insulation thickness, wire length, gravity level, and wiring methods) on the overload ignition of LDPE-insulated wires. Results demonstrated that the spontaneous ignition occurs not only in microgravity but also in normal gravity for short, thickly insulated “Sealing” cases. Core-forced ignition was more prevalent in “Unsealing” and “Pre-exposure” cases, but also occurs in long, thinly insulated “Sealing” cases in normal gravity. The ignition delay time decreases as gravity level increases, wire length increases, insulation ends become unsealed, and overload current increases. The ignition energy decreases with increasing gravity level and unsealing insulation ends, but increases with increasing wire length and higher overload current. Noted that in “Pre-exposure” cases, both ignition delay time and energy unexpectedly decrease as insulation thickness increases from 0.15 to 0.3 mm. The above tendencies were interpreted based on the motions of pyrolysis gas and deformation of the insulation, as well as 3-D numerical simulation results obtained using FDS. This work provides a valuable guidance for the design of related experimental operations. • Ignition mode map under various wire configurations and gravity conditions was draw. • The reason why IDT decreases as the insulation thickness increases was explained. • The optimal experimental design for overload-wire-ignition tests was recommended.