一种电弧引燃电缆的电气火源模拟方法

Electrical fire source simulation for igniting cable

在电缆火灾模拟试验中,火源是电缆防火性能评估的基础。现有的电气火源大多基于化学燃烧,较难反映故障电弧引燃特点。为了模拟故障电弧引燃电缆,文中开发了一种基于电弧的火源。首先,分析了110 kV电缆发生接地线被盗或两侧交叉互联线被盗等故障时金属铠装层上的感应电压,其可高达数千伏。其次,对比研究了50 Hz工频交流电压和20 kHz交流电压条件下金属护层对地电弧和雅各布天梯电弧的击穿前电压与维持电压,发现两者电弧击穿与维持特性接近。然后,提出基于雅各布天梯电弧引燃电缆的电气火源模拟方法,并实验验证了该火源能够使110 kV电缆引燃和火焰蔓延。最后,所得结论为:高频雅各布天梯电弧能够模拟故障电弧特点并有效引燃110 kV电缆。

In cable fire test,a fire source is essential for the fire performance evaluation.Most of the existing fire sources for power cable are based on chemical fuel,which is unable to represent the cable fire caused by fault arc.Therefore,to simulate the ignition of power cable by fault arc,a fire source based on electrical arc is developed in this work.Firstly,the induced voltage on the metal armor layer is theoretically analyzed when the 110 kV cable has the ground wire stolen or the cross interconnection wires on both sides are stolen.Voltages can reach thousands of volts.Secondly,the pre-breakdown voltage and sustained voltage of the metal-to-ground arc in power cable and the Jacob's Ladder arc are compared.It is found that the breakdown characteristics of both arcs are similar for applied ac voltage with frequencies of 50 Hz and 20 kHz.Thirdly,a fire source based on Jacob's Ladder arc is proposed for the ignition of power cables.Experimental results show that the 110 kV cable can be successfully ignited by this fire source,and the flame is able to spread both vertically and horizontally.Finally,the conclusion is that the high frequency Jacob's Ladder arc can simulate the characteristics of the fault arc and effectively ignite the 110 kV cable.