The calculation of setting values of timing over-current protective devices at different levels of the power system of Sanming Iron &Steel is expounded.

• 阐述了三钢集团公司内部电力系统各级定时限过电流保护定值的计算,以炼钢4%23转炉用电为例分析保护无法实现选择性的原因,并提出了解决问题的办法。