电气线路火灾频发，严重威胁着人民的生命、财产安全及生态环境，防范电气火灾任重而道远。近年来，电气火灾占比始终居于首位，高达30%。过载是引发火灾的最常见电气故障之一，是接地短路、相间短路、中性线浮动、电容击穿等多种根源性故障的最终发热表现形式。过载超温指通过导线的电流超过其额定电流值，引起导线超温。导线超温的焦耳热使导线绝缘材料发生热老化，老化后的线缆绝缘性能发生劣化，严重时可能引发绝缘击穿导致短路故障，短路电弧可以直接或间接得引燃附近可燃物，致使火灾发生。因此，开展导线过载超温热解燃烧特性与火灾危险性的研究，对于深入理解过载导线超温诱发火灾形成演化规律，评估过载超温导线的火灾危险性，更好地预防和控制电气线路火灾具有重要的科学价值和工程意义。本文选取家装常用的符合国家标准的ZR-BVR（蓝）导线作为研究对象，以1、2、3倍的额定电流加载导线1、3、6 h制备过载超温导线样品，借助相关实验设备，采用实验测试和理论分析相结合的方式，开展ZR-BVR导线过载超温热解燃烧特性与火灾危险性的系统研究，研究成果如下：

    利用热重分析仪（TG）在多升温速率下对过载超温ZR-BVR导线的热解特性进行了研究。采用无模型函数法（FWO法）分阶段计算了绝缘材料不同转化率下的活化能，并采用Málek法将实验点与理论线对比，确定了绝缘材料的热解反应机理。结果表明，在氮气气氛下，过载超温ZR-BVR导线热解过程分为三个阶段，热失重主要发生于第一阶段，失重率在57%左右。过载超温导线绝缘材料的热稳定性在焦耳热作用下有所提升，但焦耳热作用减缓了导线的质量损失速率，削弱了绝缘材料的热解强度，增加了热解残留物的剩余。无论是在热解第一阶段还是在热解第二阶段，过载超温均提升了绝缘材料发生热解反应的活化能，ZR-BVR 60·360较ZR-BVR 20·60在热解第一阶段和热解第二阶段分别增长了9.83%和10.19%。绝缘材料的热解反应机理由于受过载超温的影响表现出差异。

    借助锥形量热仪（CONE）在不同热辐射强度下对过载超温ZR-BVR导线的燃烧特性进行了研究。对比分析了绝缘材料点燃时间、总热释放量、总产烟量等燃烧特征参数随过载超温和热辐射强度的变化规律。结果表明，过载超温导线更难被点燃，ZR-BVR 60·360导线在35 kW/m²下点燃时间增长了18 s，50 kW/m²下点燃时间增长了8 s，PHRR、TPHRR和THR均出现不同程度的增加，且强过载超温增加了导线总产烟量对热辐射强度的敏感度。从燃烧特征参数看，过载超温导线虽然较难被点燃，但其点燃后表现出更高的火灾危险性。

    联用层次分析法和理想解法（AHP-TOPSIS）从多维度对过载超温ZR-BVR导线的火灾危险性进行综合评价。基于热解特性和燃烧特性的实验测试数据，通过AHP法确定各评价指标的权重，再借助TOPSIS法计算导线样品与理想解之间的相对接近度，最后根据相对接近度对评价指标赋分，根据分值评价导线的火灾危险性。结果表明，过载超温对ZR-BVR导线火灾危险性的影响受热辐射强度的影响表现出不同的效果，25 kW/m²下，过载超温增加了导线的火灾危险性，与35 kW/m²和50 kW/m²下结果相反。但综合来看，过载超温ZR-BVR导线表现出更高的火灾危险性，其中ZR-BVR 60·360导线的火灾危险性最高。另外，评价结果表明单方面评价导线的火灾危险性具有局限性，导线的火灾危险性综合热解危险、热危险和烟危险三个层次进行评价更为合理。

    Electrical circuit fire occurs frequently, which seriously threatens people's life, property safety and ecological environment, and it is still a long way to prevent electrical fire. In recent years, the proportion of electrical fires has always been in the first place, up to 30 per cent. Overload is one of the most common electrical faults that cause fires, and is the ultimate heat expression of a variety of root cause faults such as ground short circuits, phase-to-phase short circuits, floating neutral cables, and capacitor breakdowns. Overload over-temperature means that the current through the conductor exceeds its rated current value, causing the conductor to over-temperature. The Joule heat of the conductor over-temperature so that the cable insulation material thermal aging, aging cable insulation performance deterioration, which may lead to insulation breakdown resulting in a short-circuit failure, short-circuit arc can be directly or indirectly ignited nearby combustible materials, resulting in the occurrence of fire. Therefore, the study of pyrolytic combustion characteristics and fire hazard of overloaded superheated cable insulation materials has important scientific value and engineering significance for the in-depth understanding of overloaded superheated cable fire formation and evolution of the law, to assess the size of the overloaded superheated cable fire hazard, and to reduce the frequency of electrical wiring fires in daily life. This paper selects the ZR-BVR (blue) cable commonly used in home furnishing in accordance with the national standard as the research object, with 1, 2, 3 times the rated current loading cable 1, 3, 6 h preparation of overload over-temperature cable samples, with the help of related experimental equipment, using experimental testing and theoretical analysis of a combination of ways, to carry out the systematic research on the overload over-temperature pyrolysis combustion characteristics of the ZR-BVR conductor overload and the fire risk, the research results are as follows. The research results are as follows:

    The pyrolysis characteristics of overloaded and overtempered ZR-BVR conductors have been investigated using thermogravimetric analyser (TG) at multiple heating rates. The activation energy of the insulating material at different conversion rates was estimated in stages using the model-free function method (FWO), and the pyrolysis reaction mechanism of the insulating material was determined by comparing the experimental points with the theoretical lines with the help of Málek's method. The results show that under nitrogen atmosphere, the pyrolysis process of ZR-BVR cable is divided into three stages, and the thermal weight loss mainly occurs in the first stage, with a weight loss rate of about 57%. The thermal stability of the insulating material of the overloaded superheated cable was improved by the Joule heat effect, but the Joule heat effect slowed down the mass loss rate of the cable, weakened the pyrolysis strength of the insulating material, and increased the residual pyrolysis residue. Both in the first stage of pyrolysis and in the second stage of pyrolysis, the overload over-temperature elevated the activation energy of the insulating material to undergo pyrolysis reaction, which increased by 9.83% and 10.19% for ZR-BVR 60·360 compared with ZR-BVR 20·60, respectively. The pyrolysis reaction mechanism of the insulating materials showed differences due to the influence of overload superheat.

    With the help of cone calorimeter (CONE) in a variety of thermal radiation intensity of overload superheated ZR-BVR cable combustion characteristics were studied. Comparative analysis of the insulation material ignition time, total heat release, total smoke production and other combustion characteristics of parameters with the overload super-temperature and thermal radiation intensity of the changing law. The results show that the overload over-temperature cable is more difficult to be ignited, ZR-BVR 60·360 cable in 35 kW/m² under the ignition time increased by 18 s, 50 kW/m² under the ignition time increased by 8 s, PHRR, TPHRR and THR all appear to a different degree of increase, and the strong overload over-temperature increases the sensitivity of the total amount of smoke production of the cable to the intensity of thermal radiation. From the combustion characteristic parameters, the overloaded overtemperature cables showed a higher fire hazard after ignition, although they were more difficult to ignite.

    Hierarchical analysis and ideal solution method (AHP-TOPSIS) are used to comprehensively evaluate the fire hazard of overloaded and overtempered ZR-BVR conductors from multiple dimensions. Based on the experimental test data of pyrolysis characteristics and combustion characteristics, the weights of each evaluation index were determined by AHP method, and the relative proximity of the conductor samples was calculated by TOPSIS method. Finally, the evaluation indexes were assigned points according to the relative proximity and degree, and the fire risk of the conductor was evaluated according to the scores. The results show that the effect of overload over-temperature on the fire hazard of ZR-BVR conductor is affected by the intensity of heat radiation showing different effects, under 25 kW/m², overload over-temperature increases the fire hazard of the conductor, contrary to the results under 35 kW/m² and 50 kW/m². However, taken together, the overload over-temperature ZR-BVR conductor showed higher fire hazard, with the highest hazard for the ZR-BVR 60·360 conductor. In addition, the evaluation results show that the unilateral evaluation of the fire hazard of the conductor has limitations, and it is more reasonable to conduct a comprehensive evaluation of the fire hazard of the conductor by integrating the three levels of pyrolysis hazard, heat hazard and smoke hazard.