中文摘要：

对于大型水电站接地系统，由于面积巨大、分散布置、联系松散、土壤电阻率不均匀，接地材料的纵向阻抗特性可能会对接地电阻有较大影响。针对水电站接地网分布的特点，基于场路耦合方法，建立考虑接地材料影响的水电站接地网不等电位分析模型，计算分析了常用铜、钢等接地材料在不同土壤模型、电流人地点位置下的水电站接地阻抗，提出了合理利用接地材料降低巨型接地网接地电阻的措施。由计算结果可知，虽然接地材料对联系紧密的变电站接地网接地电阻基本无影响，但对大型水电站接地网接地电阻影响很大。当电流入地点位于岸上时，钢和铜接地网之间的接地电阻相差可达2倍以上。传统的接地计算公式已经不能满足实际需要，必须依靠数值分析计算来合理设计接地系统。使用铜接地材料可以明显降低水电站的接地电阻，建议在接地网骨干连接线中使用铜材，以达到经济有效地降阻。

英文摘要：

Due to the large scale, scattered arrangement, loose connection, and non uniform soil of a grounding system of hydroelectric power plant, the longitudinal impedance characteristics of grounding materials may obviously affect the grounding resistance. Consequently, according to the distribution characteristics of grounding system in hydroelectric power plants, we established a voltage-different grounding system model by taking the effects of the longitudinal impedance into consideration and using the field-circuit coupling method, and analyzed the influence of commonly used grounding materials such as copper and steel on the ground impedance of large-scale hydropower plant with different soil models and different current injected points. Moreover, we put forward a measure to reduce the ground impedance by using suitable material. The analysis results show that, although grounding material has little effect on the grounding resistance of substations, its effect on that of hydropower grounding system is remarkable. Traditional formula for analyzing the grounding system is not suitable for hydroelectric power plants, and numerical methods are necessary. When the current injected point is located on bank, the difference of the grounding resistance between copper and steel is up to more than two times. Copper electrode can significantly reduce the grounding resistance of a hydropower plant. It is recommended to use copper conductors to connect different parts of a grounding system, which is both economical and effective.