目前，我国正处于“碳达峰、碳中和”关键时期，电力资源供给正在发生革命性变革，各类电气设备被广泛应用于社会各个领域，电气火灾形势严峻。部分电气故障引发的火灾需要通过实验室的鉴定来确定起火原因，且不同电气故障产生的发热特性、温升规律、宏观组织、微观形态等方面都存在一定差异。因此，本文采用电气火灾故障模拟装置，以不同故障下插座插头的发热过程与温升规律为出发点，结合不同热辐射强度下故障熔痕特征变化规律，对固定式插座插头在过负荷、接触不良故障下，温度变化、燃烧特性、金属凝固痕迹的差异性进行实验研究与分析，研究结论可为电气火灾物物证鉴定与调查提供基础数据支撑。
首先，模拟了插座插头过电流、接触不良故障，分析插座插头的发热变化过程、最高温度及温升规律。结果表明：插座插头在不同故障下受高温产生熔融、发热、燃烧等行为，接线导线绝缘层会发生发烟、鼓泡、脱落、炭化、线芯发红等现象。此外，通电电流越大，插座插头的温度升高越明显，当通电电流≤3Ie时，因过电流故障引发火灾的可能性较小；当通电电流≥3.5Ie时，不同插座插头最终受损被破坏时的温度相似，约为260~280℃，符合大部分可燃物燃点，引发火灾的可能性较大；当电流与电阻同时增大时，插座插头温升速率明显增大，温度可达290~350℃，极易引发火灾。
其次，分析总结故障前后插座插头在不同热辐射强度下的引燃时间、热释放速率、烟气浓度等燃烧特征参数的变化规律。结果表明：随着热辐射强度的增加，插座插头的热释放速率呈逐渐上升趋势，总热释放速率逐渐增加，燃烧产生峰值的速度变快，CO2的浓度变化均呈现先减小后增大的趋势。在35 kW/m2热辐射强度下，过电流故障插座插头总热释放速率为60.32 MJ/m2，接触不良插座插头总热释放速率达到115.52 MJ/m2；在50 kW/m2热辐射强度下，过电流故障插座插头总热释放速率为181.14 MJ/m2，接触不良插座插头总热释放速率达到132.69 MJ/m2，两者差值较大，相同时间内插座插头受热面热量传递加快，导致热解速率升高。
最后，插座静片、插头插片的熔化痕迹以及绝缘层残渣是判别火灾发生原因的最有效物证，本文定量分析了故障前后插座插头熔痕的宏观结构、金相组织及微观特征规律。结果表明：在相同热辐射强度下，过电流故障插片熔痕与接触不良故障熔痕均呈现α+β两相结构，但过电流故障插片熔痕呈现不规则多边形、等轴晶结构，而接触不良故障熔痕前期仅呈现树枝晶结构。绝缘层宏观特征差异较大，外侧孔洞粗大，表面附着颗粒状杂质，绝缘层横截面呈分散状，截面相对较为平整，细小孔洞较多。在35 kW/m2热辐射强度下，接触不良故障插片熔痕的平均晶粒尺寸范围为11~17μm2，是过电流故障熔痕的4~5倍，16A三极插片熔痕的最大晶粒面积为37.58μm2，是过电流故障熔痕的1.5倍左右。插座静片熔痕孔洞内壁主要元素为Cu、Ni，熔痕表面孔洞存在少量C和Al。

At present, China is in the critical period of "peak carbon dioxide emissions, carbon neutrality", and the supply of power resources is undergoing revolutionary changes. All kinds of electrical equipment are widely used in various fields of society, and the situation of electrical fire is grim. The fire caused by some electrical faults needs to be identified by the laboratory, and there are some differences in heating characteristics, temperature rise law, macro-structure and micro-morphology caused by different electrical faults. Therefore, this paper uses the electrical fire fault simulator, starting from the heating process and temperature rise law of socket plugs under different faults, and combining with the change law of fault melting mark characteristics under different thermal radiation intensities, carries out experimental research and analysis on the differences of temperature change, combustion characteristics and metal solidification marks of fixed socket plugs under overload and poor contact faults. The research conclusions can provide basic data support for the identification and investigation of electrical fire material evidence.
Firstly, the over-current and poor contact faults of socket plug are simulated, and the heating change process, maximum temperature and temperature rise law of socket plug are analyzed. The results show that the socket plug will be melted, heated and burned by high temperature under different faults, and the insulation layer of the connecting wire will be smoked, bubbled, peeled off, carbonized and the wire core will be red. In addition, the greater the current, the more obvious the temperature rise of the socket plug. When the current is ≤3Ie, the possibility of fire caused by overcurrent fault is less. When the current is more than or equal to ≥3.5Ie, the temperature of different sockets when they are finally damaged is similar, which is about 260~280℃, which is in line with the ignition point of most combustible materials and is likely to cause fire. When the current and resistance increase at the same time, the temperature rise rate of socket plug increases obviously, and the temperature can reach 290~350℃, which is easy to cause fire.
Secondly, the changing rules of combustion characteristic parameters such as ignition time, heat release rate and smoke concentration of socket plug under different thermal radiation intensity before and after the fault are analyzed and summarized. The results show that, with the increase of thermal radiation intensity, the heat release rate of socket and plug is gradually increasing, the total heat release rate is gradually increasing, the speed of combustion peak is faster, and the change of CO2 concentration is first decreasing and then increasing. Under the thermal radiation intensity of 35 kW/m2, the total heat release rate of over-current fault socket plug is 60.32 MJ/m2, and the total heat release rate of poor contact socket plug reaches 115.52 MJ/m2. Under the thermal radiation intensity of 50 kW/m2, the total heat release rate of over-current fault socket plug is 181.14 MJ/m2, and that of poor contact socket plug is 132.69 MJ/m2, which is quite different. In the same time, the heat transfer of socket plug heating surface is accelerated, which leads to the increase of pyrolysis rate.
Finally, the melting trace of socket static piece, plug insert and insulation residue are the most effective evidence to judge the cause of fire. This paper quantitatively analyzes the macro-structure, metallographic structure and micro-characteristics of the melting trace of socket plug before and after the fault. The results show that, under the same thermal radiation intensity, both the overcurrent fault insert weld and the poor contact fault weld show α+β two-phase structure, but the overcurrent fault insert weld shows irregular polygon and equiaxed crystal structure, while the poor contact fault weld only shows dendrite structure in the early stage. The macro characteristics of insulation layer are quite different, with large holes on the outside and granular impurities attached to the surface. The cross section of insulation layer is dispersed, relatively flat and many small holes. Under the thermal radiation intensity of 35 kW/m2, the average grain size range of the weld mark of the fault insert with poor contact is 11~17μm2, which is 4~5times of the weld mark of the overcurrent fault, and the maximum grain area of the weld mark of the 16A triode insert is 37.58μm2, which is about 1.5 times of the weld mark of the overcurrent fault. The main elements in the inner wall of the weld mark hole of the socket stator are Cu and Ni, and a small amount of C and Al exist in the weld mark surface hole.

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