Performance Testing and Analysis of HVDC Deep-well Grounding Electrode

As an important part of the HVDC project, the grounding electrode provides a path for the ground current and unbalanced current. Shallow-buried grounding electrode covers a large area, has few optional pole sites, and is difficult to select, especially in the southeast coastal areas of P. R. China. The grounding electrode site location is often far away from the converter station for a long distance, resulting in the grounding electrode line as long as hundreds of kilometers, which increases the project investment and subsequent operation and maintenance costs. Therefore, the research on deep well grounding electrode technology is proposed. The advantage of the deep-well grounding electrode of HVDC is that it covers a small area, which will help to solve the problem of site selection. The fist kilometer deep-well grounding electrode has been built by China Southern Power Grid (CSG), and it has been connected to HVDC system and put into testing operation for about one year. Various project performance tests of deep well grounding electrode, such as grounding resistance, step potential difference, touch potential difference, potential distribution, and characteristics of temperature rise, were carried out during this period. This paper analyzes these tests contents in detail. The results show that the overall performance of the deep-well grounding electrode is stable, it can save 90% of the site area, reduce 2/3 of the resistance and 80% of the contact potential.