110kV全户内智能变电站接地网优化设计

摘要

全户内智能变电站占地面积小,入地短路电流高,虽然城区土壤电阻率相对较低,但接地电阻和地电位升仍难以降低.以某110kV全户内变电站土壤模型为例,对新一代智能变电站典型设计方案110-A2-X1的接地网进行优化设计.优化设计时,通过分析设计规范对接地参数的要求,适当放宽接地网地电位升高的限值;基于CDEGS接地分析软件,分析不同面积和网孔尺寸的双层地网的降阻效果,以及不同数量和长度深井接地极的降阻效果,并对应用了双层地网和深井接地极的优化方案进行安全性评估和经济性比较.结果表明,与双层地网相比,接地深井虽然成本较高,但降阻效果良好,对于无人值守的110 kV全户内智能变电站,选取6口55m的接地深井的降阻方式形成其接地网优化方案可满足各项安全性要求.%Because of the small area and high level of ground fault current in today's whole-indoor urban intelligent substation,it is difficult to decrease the grounding resistance and the grounding potential rise,even with the low soil resistivity.Based on a soil model of a 110kV whole-indoor substation,the optimal grounding grid of a whole-indoor intelligent substation 110-A2-X1 is designed.In the process of optimal design,the threshold for grounding potential rise was relaxed appropriately by analyzing the requirements for grounding parameters in design code.The resistance reduction effects of two-layer grounding grid and deep-well grounding electrodes of different numbers and length were investigated with CDEGS software,and the safety and economy of the two resistance reduction measures were compared.The results show that the grounding deep-well has high cost but good resistance reduction effects compared with the two-layer grounding grid.And for unattended 110kV whole-indoor intelligent substation,it is suggested to use six grounding wells each with a depth of 55m for grounding grid o reduce the resistance.