中文摘要：

变电站接地网的拓扑结构由于输电线路架空地线或两端接地电缆的接入会发生改变,测量得到的接地阻抗已不是运行变电站主接地网的接地阻抗。为此基于场路结合的思想,提出了分步计算运行变电站接地网接地阻抗的方法。通过算例分析比较,验证了该计算方法的准确性和计算模型的正确性。对影响计算的主要因素进行分析表明：电流注入点和架空地线出线回数有较大影响。对比了3种不同条件下架空地线及杆塔对计算精度的影响,提出测量运行变电站接地网接地阻抗时,电流注入点不宜选在地网边角;架空地线回数较多时,需考虑终端塔对测量结果的影响。

英文摘要：

Topology structure of a grounding grid in substation will change due to the overhead grounding wire of transmission lines or two-end grounded power cables connected with the grounding grid.Consequently,the measured grounding impedance of a grid will be different from the actual value of the main grounding grid of substation in operation.Therefore,on the basis of the idea of field-circuit coupling theory,we put forward a step-by-step method to calculate the grounding impedance of substation in operation.The accuracy of the calculation method and the correctness of the model were validated by an example analysis and comparison.An analysis of the main factors affecting the calculation shows that the current injection point and the amount of overhead grounding wires have considerable influences on the grounding impedance calculation.Moreover,the impact of grounding wire and tower on the calculation accuracy under three different conditions are compared,and the results indicate that the current injection point should not be in the corners of a grounding grid when measuring the grounding impedance of substation in operation;if there are many lightning lines,it is necessary to consider the impact of the terminal tower on the measurement results.