Conductivity Property of Frozen Soil in Alpine and High Altitude Regions up to 5500m

In the future of China, the UHV AC and DC lines will pass through more high-altitude areas, among which the highest altitude of the UHV AC project is close to 5000m, and the highest altitude of the UHV DC project is close to 5500m. The overall improvement of the altitude poses new challenges for the design and construction of the UHV lines. At high altitude, the geographical environment is complex. The climate is harsh. There is frozen soil. The soil resistivity is high, and it is greatly affected by the season and climate. The grounding devices of a large number of transmission lines are in bad soil condition, which greatly affects the current dispersion effect of the grounding body, resulting in high grounding resistance and difficulty in reducing resistance. Therefore, the grounding reliability of the power system is greatly reduced, threatening system safe. At present, there is little research on the electrical conductivity of frozen soil at home and abroad. This paper introduced the basic physical properties of frozen soil, including its material composition and water holding capacity, gave the conductive mechanism of frozen soil, and made an experimental study on its conductive performance. The test results showed that the electrical conductivity of soil was related to many factors. The main influencing factors were soil type, water content (amount and phase state of soil water) and soil salt content (the type and amount of electrolyte salt in soil). To frozen soil, temperature was another very important factor. The relationship between many influencing factors is complex. As the soil resistivity representing the conductivity of frozen soil, it is the result of the comprehensive influence of various factors. When evaluating the conductivity of frozen soil, the influence of various factors should be comprehensively considered.