Study on the Applicability of Flexible Graphite Grounding Body and Grounding Module for 500kV Transmission Line in High Altitude Area

Sichuan-Tibet Railway Changdu-Linzhi section construction power supply project (Phase II) by Tibet Power Grid Co. 4900m), the mountain is treacherous, the foundation excavation is difficult (mostly rock foundation). Among them, 3 times across 35kV lines, 1 time across 220kV lines, 1 time across the Nujiang River, across the construction is more difficult. At present, China often use galvanized steel, galvanized copper and other traditional grounding materials, due to corrosion phenomenon caused by the increase in grounding resistance, affecting the frequency current, lightning current dispersion, but also cause local stride voltage and contact voltage does not meet the requirements of the regulations, generally in 8 years need to be replaced, which greatly increases the construction cost. In order to ensure the safe operation of power equipment and the safety of staff operation, stable and highly reliable grounding materials are needed. In recent years, flexible graphite material is widely used in grounding engineering, which has good electromagnetic characteristics and strong chemical stability, not easy to be eroded by the environment, and can operate in the grounding of power equipment in a long-term and stable manner. In this paper, the soil geological structure and typical line tower grounding resistance in Tibetan area are tested and analyzed, and the flexible graphite grounding material is applied to the grounding transformation of line tower in combination with local problems in Tibet, which can reduce the burial depth of grounding electrode, and compared with the solution of using traditional grounding material, it can reduce the cost and improve the project progress, and help the construction unit and construction unit to control the budget and construction period.