直流接地极与大地中金属管道的防护距离

针对直流输电工程接地极对地下金属构件的腐蚀问题，对电腐蚀的特性进行了分析，确定了大地金属构件腐蚀的限值。因海岸与陆地直流接地极计算模型不同，考虑到海洋面积远大于陆地面积，且海水的电阻率远小于大地土壤电阻率，对附近大地电位的分布影响较大，因此海岸直流接地极应根据周围的地质环境建立计算模型。考虑到海洋对大地电位的影响，对大地土壤电位梯度进行了计算，预估了海岸直流接地极与地下金属构件的防护距离。

Protective Distance between HVDC Electrode and Underground Metal Pipeline

In view of the corrosion of underground metal components caused by the grounding electrode of HVDC power transmission project, the features of electro-corrosion are analyzed and the limit values of corrosion to grounding metal components are determined. Due to the difference between the calculation model for HVDC grounding electrode on shore and in land and considering that the area of sea is far more than that of land as well as the resistance of seawater is far less than specific resistance of soil in the land so the latter has greater influence on the distribution of adjacent ground potential, thus the calculation model for HVDC grounding electrode buried into the shore should be established according to peripheral geological environment. Taking the impact of the sea into account, the potential gradient of soil in the land is calculated and the protective distance between HVDC grounding electrode buried into the shore and underground metal components are pre-estimated.