Experimental study on microstructure of overcurrent fault of copper conductor

Abstract

This study aims to more accurately identify the microstructure characteristics of copper wire when overcurrent fault occurs, and further improve the accuracy of electrical fire investigation. In this paper, the overcurrent fault of copper conductor under 4-7 times rated current is simulated. The difference of metallographic structure under different current is analyzed by metallographic microscope. Image-Pro-Plus software is used to measure grain perimeter, and the quantitative criterion and change rule of metallographic structure are studied. The experimental results show that with the increase of current, the diameter and area of the grains tend to increase. When Ie=128A, the grains are mainly slender dendritic and columnar, accompanied by a small amount of cellular crystal distribution. The grain directions are different, and the boundary between grains is large; when Ie=160A, the grains continue to grow, the number of dendritic crystals increases, and the grain boundary becomes fine; when Ie=192A, the grains are mainly columnar and cellular, with clear grain boundaries, obvious lattice and generally consistent grain directions; when Ie=224A, the dendritic grains decrease obviously, and the grain diameter and area have little change compared with 192A.