Flame extinction over electrical wires under transverse flow: Critical damkohler number analysis incorporating solid-phase heat conduction

The world is currently undergoing a global transition, moving away from fossil fuel energy towards electricity-driven energy sourced from renewables. Electrical wires in the power systems, crucial for energy transmission, face significant fire risks. To accurately predict the flammability limits of electrical wires, it is necessary to consider the effect of heat loss, particularly caused by solid-phase conduction on blow-off extinction, which is currently not well understood. This paper addresses this knowledge gap by systematically investigating the flame extinction of upward- and downward flame spread over vertical electrical wires under transverse flow. Ten types of wires with copper and nickel-chrome cores were tested. Results show the wires with a higher thermal conductive core reach blow-off limits at lower velocities. Unique local extinction near the pyrolysis front occurs in downward spread. Strain rate fails to converge blow-off limits, emphasizing role of solid-phase conduction. Critical Damkohler analysis predicts blow-off limits, incorporating metal core temperature. As flow velocity increases, a critical Da value of 17.7 predicts blow-off for PE-insulated wires. This study presents a comprehensive approach for elucidating blow-off extinction by incorporating solid-phase conduction, and can provide a reference basis for the material selection of wires in the electrical power system.