一次6kV厂用电系统接地的故障分析及整定计算

Fault Analysis and Setting Calculation on the 6kV Ground Fault

通过一次6kV高压厂用系统发生单相接地故障时启备变和高厂变分支零序过流保护均拒动的实际案例,提出启备变高厂变分支零序过流保护在整定计算时,不仅需要按照相关规程和标准规定的方法进行整定计算,而且要结合现场实际情况和一次接线方式进行深入研究。针对忽略容性电流、考虑停机状态时的容性电流和开机状态时的容性电流3种运行方式,用Multisim软件仿真计算出故障电流,并与实际故障电流比对,总结出故障电流的分布特征,提出了3种定值整定方法,分析了各方法的优缺点,选择出最佳方案,确保了保护动作的正确性,达到了优化保护定值,提高保护动作可靠性的目的。

Through the practical case of branch zero sequence over-current protection of start up/standby transformer and HV station transformer refuse operation when 6 kV ground fault happening,this article points out that the setting calculation not only needs to comply with the relative regulations and standardized methods,but also should combine with the status quo and the primary connecting mode.It puts forward three different situations to calculate fault current,using Multisim software.In comparison with actual figures,it summarizes distribution characteristics of fault current,chooses the best proposal,which ensures the correctness of protection,optimizes the protection setting value,and improves the reliability of protection.