Analysis of Synthetic Electric Field in Long-span Section of AC to DC Transmission Line

With the development of energy Internet and smart grid, long-span DC transmission lines have received widespread attention as an important supplement to traditional AC transmission lines. Long-span DC transmission lines have the advantages of strong transmission capacity, long transmission distance and low transmission loss. However, after the AC transmission line was changed to DC operation, the height and structure of the foundation tower of the large span section remain unchanged, The spatial electric field distribution of AC/DC transmission lines is also different. Therefore, it is necessary to explore the synthetic electric field of the large span section of the DC line to avoid affecting the reliability of the line and the operational safety of the ship. Based on existing AC transmission line parameters, In this paper, an electromagnetic simulation model for long-span cross-section of transmission conductor lines is established. Under the operation mode of seven HVDC transmission lines, The synthetic electric field strength of the line surface, the rich height of the ship's safe navigation and the electric field strength of the river surface were explored. The simulation results show that the electric field on the surface of the wire is directly related to the operation mode, and the transmission line with the middle crossbar does not operate and only the middle crossbar conductor is running, which increases by 55.9% and 31.8% compared with the operation of the three-way conductor, and it is necessary to pay attention to air ionization and discharge. The size of the synthetic electric field at the operating height of the ship and at the river surface under the seven operation modes is less than the national standard of 25kV/m.