| 论文中文题名： | 铝合金导线过电流故障演化过程及熔痕微观组织研究 |
| 姓名： | |
| 学号： | 17220214058 |
| 保密级别： | 公开 |
| 论文语种： | chi |
| 学科代码： | 085224 |
| 学科名称： | 安全工程 |
| 学生类型： | 硕士 |
| 学位年度： | 2020 |
| 培养单位： | 西安科技大学 |
| 院系： | |
| 专业： | |
| 研究方向： | 消防科学与工程 |
| 第一导师姓名： | |
| 第一导师单位： | |
| 论文外文题名： | Investigation of the Evolution Process and Microstructure of Molten Marks after Overcurrent Fault of Aluminum Alloy Wire |
| 论文中文关键词： | |
| 论文外文关键词： | Fire investigation ; Aluminum alloy wire ; Overcurrent fault ; Molten marks ; Microstructure |
| 论文中文摘要： |
铝合金导线因性价比高、抗氧化性强和密度低等优势广泛应用于高压输电线路及供电干线，当电气系统中发生短路、中性线浮动和雷击等故障均会诱发导线电流增大。针对铝合金导线过电流故障演化过程及熔痕微观特征不明的问题，本文分析了铝合金导线过电流故障发热现象和电弧演变过程，探究了电流和绝缘层对过电流故障熔痕显微组织的影响，对比分析了铝合金导线、铝导线和铜包铝导线过电流故障熔痕的微观组织特征。研究结论对电气火灾物证鉴定技术具有科学和实践意义。
采用电气故障模拟实验装置，模拟了128 A–224 A电流条件下铝合金导线过电流故障，利用非接触式高速红外热像仪捕捉导线实时温度。研究结果表明，随着电流增大导线升温速率增加，熔断时间减小，铝合金导线绝缘滴落至少需要160 A电流。绝缘导线与裸导线发热过程不同，裸导线的升温速率大于绝缘导线，熔断温度比绝缘导线低29.68 ℃，熔断时间缩短了17.4 s，数值计算导线温度时应考虑绝缘层对导线温度的影响。在焦耳热作用下线芯熔断后导线端部依次产生金属电弧和气体电弧，电弧熔痕形成过程受电弧热-力共同作用影响。
利用金相显微镜和扫描电子显微镜等测试手段表征了铝合金导线电弧熔痕微观组织，通过Image-Pro-Plus量化晶粒参数。实验结果表明，额定电流时第二相弥散分布在铝合金导线本体，过电流故障后电弧熔痕第二相消失，晶粒结构为胞状树枝晶，晶界存在成分偏析现象，随着电流增大，晶粒的平均粒径逐渐减小。裸导线与绝缘导线电弧熔痕金相组织相同，但是裸导线电弧熔痕孔洞内无Cl、Ca元素。
最后从金相组织、物相结构及元素成分等角度，对比分析了铝合金导线、铝导线和铜包铝导线过电流故障熔痕微观组织特征。研究发现，铝合金导线与铝导线熔痕金相组织结构相同，第二相对铝合金导线熔痕晶界有细化作用，铝导线熔痕晶界处存在结晶相。铜包铝导线电弧熔痕组织为共晶结构，电弧熔痕，过渡区及导线本体随着温度减小初生α-Al相和α+β共晶结构比例减小。研究还发现铝合金导线，铝导线及铜包铝导线过电流故障电弧熔痕物相结构不同。
|
| 论文外文摘要： |
Aluminium alloy wire is widely used in high-voltage transmission lines and power supply main lines due to its high cost performance, strong oxidation resistance and low density. When short circuit, neutral line floating and lightning strike occur in the electrical system, overcurrent faults will occur in the wire.For aluminum alloy wire overcurrent fault evolution and molten marks of unknown problems, this paper analyses the overcurrent fault wire heating phenomenon and the evolution of the arc, and explores the current and insulation influence of the microstructure of molten marks after overcurrent fault.compared the aluminum alloy wire, aluminum wire and copper clad aluminum wire overcurrent fault microstructure characteristics of the molten marks.The conclusions are of scientific and practical significance to the identification of material evidence of electrical fire.
An electric fault simulation experiment device was used to simulate the overcurrent fault of aluminum alloy wire under the current condition of 128 A–224 A.The results show that with the increase of current, the heating rate of the wire increases, and the melting time decreases, insulation dripping requires at least 160 A currents. The heating rate of bare wire is higher than that of insulated wire, the fuse temperature is 29.68 oC lower than that of insulated wire, and the fuse time is reduced by 17.4 s, the influence of insulation layer on wire temperature should be considered when numerical calculating wire temperature. Metal arc and gas arc are produced at the end of the wire after the core is fusing under joule heat. The forming process of arc beads is the result of thermodynamic action.
The microstructure of arc beds of aluminum alloy was characterized by optical microscope and scanning electron microscope, and the grain parameters were quantified by Image-Pro-Plus. The results showed that the microstructure of aluminum alloy wires was distributed in the second phase at rated current, and the second phase of arc fusion trace disappeared after overcurrent fault. The grain structure was cellular dendritic, and there was composition segregation at grain boundary. The metallographic structure of arc beads of bare wire and insulated wire is the same, but there is no Cl and Ca element in arc beads hole of bare wire.
Finally, the microstructure characteristics of overcurrent fault metal melt trace of aluminum alloy wire, aluminum wire and copper clad aluminum wire were compared and analyzed from the metallographic structure, physical phase structure and element composition.It is found that the microstructure of the aluminum alloy wire is the same as that of the aluminum wire, the grain boundary of the second alloy wire has thinning effect, and the crystal phase exists at the grain boundary of the aluminum wire. The microstructure of arc beads of copper clad aluminum wire is eutectic structure, and the proportion of primary α-Al and α+β eutectic structure decreases with the decline of temperature. It is also found that the phase structure of arc beads of aluminum alloy wire, pure aluminum wire and copper clad aluminum wire is different.
|
| 中图分类号： | TM201.4 |
| 开放日期： | 2020-07-23 |
谷歌
火狐
