Studies On The Electromagnetic Environment For HVDC And AC-DC Parallel Transmission Lines

Because of the rapid growth of electricity demand and geographic maldistribution of resources, long-distance and high-capacity transmission lines have become an important part of the power system. Meanwhile, the shortage of transmission corridor makes AC and DC parallel transmission system become necessary.With the gradual increase in environmental awareness, the impact of transmission lines on the environment has been paid increasingly attention. Especially for the high-voltage transmission projects, high voltage and large capacity make the impact more obvious. The electromagnetic environment influences of AC and DC transmission lines include electric and magnetic fields, radio interference and audible noise. The electric field of DC lines is different from AC's. Ion flow and total electric field generated by corona will produce particular problems. AC and DC transmission lines will interact; the corona onset voltage and the distribution of electric field would be changed. The surrounding environment needs to be Re-evaluated.In this paper, based on Ningdong-Shandong±660 HVDC project, modeling simulation and assessment of electromagnetic were given; conductor surface field strength, distribution and influence factors of total electric field and ion current density were analyzed. And on this basis, the mixed electric field of AC and DC transmission lines in one corridor and on the same tower was discussed and analyzed. These conclusions providing effective technical support and reference could also accumulate data for further research and construction of parallel transmission lines.Through the calculation in this paper, for Ningdong-Shandong±660 HVDC project, the value of total electric field on the ground, ion current density, radio interference and audible noise were lower than the limits set by the state. Meanwhile, the influences of line-to-ground height, electrode distance and a series of structural parameters were analyzed. And the model of AC-DC parallel lines was established for calculating its hybrid electric field strength compared with the state limit. The analysis and the conclusion could provide direct data reference for controlling the electric field strength of parallel lines.