含电缆出线变电站内短路电流分流系数仿真分析

Analysis of Affecting Factors on Fault Shunt Coefficient in Substation with Cable Outlets

变电站内发生短路故障时,真正会对变电站造成危害的是通过变电站地网入地的电流,因此研究短路电流的分流系数有重要意义。电力电缆结构与架空线不同,二者的分流系数存在较大的差别。基于PSCAD软件,仿真计算了含电缆出线的变电站发生短路的地网分流系数,探讨了电缆长度、交叉互联等因素对分流系数的影响。计算结果表明,当变电站出线为电缆线路时,发生短路时地网分流系数远小于架空线路,减小了对变电站地网的分流要求,但同时也会导致短路电流增大,两者应当综合考虑。

While a short-circuit fault occurs in a substation,it's the current diffused into ground that actually causes the safeness trouble and hence it's important to study the fault shunt coefficient.The structure of cables is different from that of the overhead lines so that the shunt coefficient is distinct.This paper adopts PSCAD to calculate the fault shunt coefficient in the substation with cable outlets,and analyzes the influencing factors including the length of the cables,cross-bonding etc.The results show that the fault shunt coefficient of the substations with cable outlets is far lower than that of substations only with overhead lines,and therefore the requirement for the shunt capability of grounding grids is reduced.But at the same time,it will cause larger short-circuit current,so overall consideration is needed.