Research On The Space Electric Field Around HVAC-HVDC Hybrid Transmission Lines

As the transmission line corridors become more and more rare in China, it is now inevitable to construct HVAC-HVDC hybrid transmission lines. The research on the electric field around the HVAC-HVDC hybrid transmission lines plays an important role in evaluating the electromagnetic environment.HVAC and HVDC line separated in parallel or in the same tower will affect each other. The research use instantaneous value to calculate the surface voltage gradient on the transmission lines and the electric field on ground. Both sub conductors of HVAC & HVDC are settled in one system in order to consider their mutual influence.This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images. For the calculation of electric field on ground under AC transmission line, equivalent charge method is used, while for the electric field at the ground level under DC transmission lines, Deutsch assumption method is used. The research improved Deutsch assumption method in order to calculate the electric field on ground in rain weather. Furthermore, the calculation results are compared with that from documentary in order to validate the reliability of the improved method.Finally, the paper studied factors influencing surface voltage gradient and the electric field on ground, including radius and separated number of sub-conductor, configuration of transmission line(in parallel or on the same tower), and weather condition( fine or rain). The results indicate that, effect measures can be taken to reduce the space electric field as follows: reducing radius or increasing separated number of sub-conductor, positive DC polar neighboring AC line in parallel corridor and DC above ac line in same tower configuration.