Coupling between DC lines with a neutral conductor and parallel ac lines

HVDC lines may have use the same right of way as ac lines. This paper discusses the general study methodology that can be used to investigate any coupling between dc and ac transmission lines that share the same right-of-way. The capacitive coupling and the inductive coupling between a dc line with a long neutral conductor and an ac transmission system running parallel to it were investigated. A digital simulation model of the coupling phenomenon was developed to model the induced fundamental frequency voltage on the dc line and the neutral conductor. The induced dc current in the converter transformer secondary winding was also modelled.