Research On Electromagnetic Coupling And Improvement Measures For Uhv Transmission Lines Erected In The Same Corridor

With the economy developing rapidly, the demand of society for electricity is growing. In order to improve the transmission capacity of the transmission corridor and mitigate the contradiction between the corridor construction and land shortage, it has become an inevitable trend that UHV transmission lines are erected in the same corridor. There is strong electromagnetic coupling effect between the UHV transmission lines erected in the same corridor, as a result of it, the inducted voltage and inducted current pose a great threat to the safety of maintenance personnel and transmission and transformation equipment in the power system. So the research on interference due to electromagnetic coupling between UHV transmission lines erected in the same corridor.In this paper, a electromagnetic coupling model containing two circuits of500kV AC transmission lines and single circuit of±800kV transmission lines erected on the same tower is established. The influencing rule of AC lines arrangement, load current, running condition and DC lines transposition on the electromagnetic coupling of DC lines is researched. A improvement measure for the electromagnetic coupling between transmission lines is proposed—erecting coupling ground wires. When coupling ground wires are erected beneath HVDC transmission lines, the influences of the spatial distribution of coupling ground wires on voltage induced on HVDC transmission lines are simulated and analyzed based on the improved model. Research results show that the coupling ground wires have a good shielding effect on electromagnetic coupling effect between transmission lines, and the spatial distribution of coupling ground wires has a large impact on the shielding effect.The influence of electromagnetic coupling effect between UHV transmission lines erected in the same corridor on power system is studied, including DC magnetic biasing characteristic of converter transformer for AC/DC corridor-sharing power transmission system and the current imbalance of double-circuit UHVAC transmission lines erected on the same tower. A DC magnetic biasing model for converter transformer and a transmission line model of1000kV single-circuit AC and±800kV single-circuit DC corridor-sharing power transmission system are built, and the DC quantities due to ground potential of the soil and power frequency induction of AC/DC transmission line are calculated respectively; the influencing rule of parallel erected lengths of AC/DC transmission lines and the approach distance between the centers of AC and DC transmission towers on DC magnetic biasing in converter transformer is researched. Research results show that the longer the parallel erected lengths of AC/DC transmission lines and the closer the approach distance between the centers of AC and DC transmission towers, then the larger the DC magnetic biasing in converter transformer is, and the higher proportion of DC magnetic biasing due to power frequency induction in the total DC biasing, the lighter impact of ground potential of the soil on this proportion will be. The model of1000kV UHV double-circuit AC transmission lines on the same tower is established, the influence of electromagnetic coupling between transmission lines on the current imbalance is studied. The results show that: the current imbalance is large when one of the two lines is heavily loaded while the other is lightly loaded, and the current imbalance is small when both of two lines are heavily loaded.