Experimental Study On The Suppressing Radio Interference Of DC Transmission Lines By Magnetic Rings

High Voltage Direct Current (HVDC) system has a series of special advantages, such as long-distance transmission, large capacity, and point-to-point transmission. HVDC has become an important component the grid. However, with the increase of voltage levels, radio interference (RI) produced by the corona discharge has become a restraining factor of the power grid’s design and operation. Currently, measures of weakening and suppressing corona effect are mostly passive. But all the above measures are high-cost. Optimizing and changing the structure parameters of transmission lines, to a certain extent, could reduce RI values. But these measures have a slight inhibition effects at high costs. In this paper, a new idea for suppressing radio interference of DC transmission lines by ferrite rings is put forward. Because of their good high-frequency characteristics, ferrite rings are widely used in the field of electromagnetic compatibility.Firstly, this paper describes magnetic materials’, classification, the main parameters and their physical meaning. And this paper also tests different kinds of ferrite rings by precision impedance analyzer. Then this paper has stated the principle of magnetic rings suppressing corona current’s spread and RI. Depending impedance characteristic data by impedance analyzer tests, the paper makes a calculation and Matlab simulation that magnetic rings suppress corona current’s spread, and tests for magnetic rings suppressing corona current’s spread. At last, DC conductor corona discharge high-voltage test platform is set up. The single-point corona discharge conductor and stranded were set wire as the test conductor respectively. Then the paper analyzes inhibition effects and laws among different conditionsA large number of simulation and experimental results in this paper show that magnetic rings based soft ferrite material have a good inhibitory effect of suppressing DC line corona current’s spread and RI. Different magnetic materials have obviously different impedance characteristics, and inhibitory effect laws. Inhibition effects at negative voltage are better than positive voltage. With the increasing number of magnetic strings, the inhibitory effect increases insignificantly.This paper has laid the foundation for further research to suppress RI of actual HVDC lines, and even AC line’s radio interference suppression. At the same time, the paper has also good prospects of practical significance and engineering.