Electrical wire is one of the primary causes of electrical fires because of short circuiting or overload current. Experiments were carried out to characterize the influence of high currents on flame spread and dripping behaviors over wires. Two samples of polyethylene (PE)-insulated copper wires with different sizes (d_c/d_o = 0.9 mm/3.0 mm for wire #1 and 1.3 mm/4.2 mm for wire #2) were electrified with current, ranging from 10 A to 50 A, to conduct experimental study. Results show that the dripping becomes faster as the current increases and the continuous dripping occurs under high current (I > 40 A for wire #1 and I > 30 A for wire #2), causing the flame to be narrower and shorter. The heat transfer by different passages (radiation, convection, conduction through core and the joule heat) were quantitatively analyzed. The heat feedback from core to the insulation (${\dot{q}}_{cp}$) were the dominant heat transfer mode during flame spread over energized wire. Heat required for flame spread (${\dot{q}}_{req}$) is mainly supplied from the core, nearly 80%, including the joule heat (${\dot{q}}_{joule}$) and the heat conduction through the core from the burning zone (${\dot{q}}_{cc}$). The proportions ${\dot{q}}_{cp}/{\dot{q}}_{req}$ decreased with the increasing current, and has a sharp decent to 70% or 50% at I = 50 A or 35 A for wire #1 or wire #2, respectively. In addition, the proportion of ${\dot{q}}_{cp}$ to the sum of ${\dot{q}}_{joule}$ and ${\dot{q}}_{cc}$ drops obviously under high current, which means the dominated role of core heat feedback in heat transfer mode is weakened under high current. A flame spread model for energized wire based on the quantitative analysis of controlling heat transfer mechanism was proposed, and it predicted the flame spread rate well within error of ±20%. The findings of the presented study will be essential for simulation study of flame spread behavior over energized wires with high current and may guide the design of future electric fire safety.

由于短路或过载电流，电线是引起电气火灾的主要原因之一。进行了实验以表征高电流对电线上火焰蔓延和滴落行为的影响。两种不同规格的聚乙烯（PE）绝缘铜线样品（d _c / d _o = 0.9 mm/3.0 mm 的导线 #1 和 1.3 mm/4.2 mm 的导线 #2) 通电，电流范围从 10 A 到 50 A，以进行实验研究。结果表明，随着电流的增加，滴落变得更快，并且在高电流（I > 40 A 的电线 #1 和 I > 30 A 电线#2）下发生连续滴落，导致火焰更窄和更短。定量分析了不同通道（辐射、对流、核心传导和焦耳热）的传热。从核心到绝缘的热反馈（${\dot{q}}_{C磷}$) 是火焰在通电导线上蔓延期间的主要传热模式。火焰蔓延所需的热量（${\dot{q}}_{r\mathrm{电子}q}$) 主要由核心提供，近 80%，包括焦耳热 (${\dot{q}}_{j○你升\mathrm{电子}}$) 和从燃烧区通过核心的热传导 (${\dot{q}}_{CC}$）。比例${\dot{q}}_{C磷}/{\dot{q}}_{r\mathrm{电子}q}$随着电流的增加而降低，并且在I  = 50 A 或 35 A 时，导线 #1 或导线 #2 分别急剧下降至 70% 或 50% 。此外，占比${\dot{q}}_{C磷}$ 总和 ${\dot{q}}_{j○你升\mathrm{电子}}$ 和 ${\dot{q}}_{CC}$大电流下显着下降，这意味着在大电流下核心热反馈在传热模式中的主导作用减弱。提出了一种基于传热机理控制定量分析的通电导线火焰蔓延模型，预测火焰蔓延速度误差在±20%以内。所提出的研究结果对于模拟研究高电流通电导线上的火焰蔓延行为至关重要，并可指导未来电气防火安全的设计。