Radio interference on DC lines from HVDC convertor stations

An assessment has been made of the RF power generated by a modern thyristor-valve convertor station and injected onto a DC transmission line. The total AC power and the power spectrum have been determined for each pole. At a 400 MW (0.4 p.u.) load on the Dickinson, Minnesota, station the RF power per pole launched on the DC system is of the order of 100W for the 10 kHz¿¿30 kHz range and 20W above 30 kHz. As there is no reference for comparison, this result was quite interesting. The effect of the physical configuration of the 3-phase valve components on ignition pulse amplitude was observed. This work provides some insight into the inverter operation of a convertor station when viewed as an RF source.