Theoretical Study on Radio Interference of HVDC Transmission Line Based on Cage Tests

Due to the effect of the space charges, there is still a lack of effective methods to predict the corona effects of HVDC transmission line based on cage tests. This paper presents a method of using the corona cage to evaluate the radio interference of HVDC transmission lines. First, the condition under which the tests of a corona cage can be equivalent to those of an HVDC transmission line is discussed theoretically. It shows that the key is to make the electric-field distribution around the conductors in the corona cage the same as that around the transmission line. Then, a numerical approach and the Kaptzov's assumption are used to obtain the applied voltage on the conductors in a corona cage in order to set up the same electric-field distribution as that around the transmission line. Reduced-scale tests both in time domain and in frequency domain show that the method is effective. The method can also be extended to investigate the dc corona and its other effects based on cage tests.