根据GB/T 3953-2009和GB/T 4909.3-2009，对原始标距为200 mm和250 mm的电工圆铜线进行了多组拉力试验以及不确定度评定。结果表明：短标距试样的断后伸长率大于长标距试样的断后伸长率，而抗拉强度相差不大；两种标距试样断后伸长率和抗拉强度的标准扩展不确定度几乎一致。建议在拉力测试时使用短标距试样。

According to GB/T 3953-2009 and GB/T 4909.3-2009, multi-group tensile tests and uncertainty assessment were carried out on the electrical round copper wires with initial gauge length of 200 mm and 250 mm respectively. The results show that the percentage elongation after fracture of samples with short gauge length was larger than that of samples with long gauge length, and there was little difference in tensile strength. Standard extension uncertainty of elongation after fracture and tensile strength of two kinds of samples were virtually identical. It is recommended to use short gauge specimen in tensile test.