Analysis of electromagnetic interference on DC line from parallel AC line in close proximity

As the need for electric power grows continuously, transmission systems with more delivery capability, such as HVDC lines, are also needed. However, one of the biggest obstacles to construct a new transmission system is the obtaining of sufficient right-of-way, due mainly to the economical and ecological reasons. As a consequence, ac and dc transmission lines are to be built in parallel sharing the same right-of-way. In this paper, the electromagnetic interference in a dc line, due to the capacitive and inductive coupling from a parallel ac line in close proximity, is studied in detail. A multiconductor transmission line model is elaborated in the electromagnetic transient program to calculate the induced voltage from an ac line upon a dc line. A method based on Fourier series theory, to obtain the direct current flowing into the converting transformer, is presented. The generated interferences upon the dc line are calculated and analyzed through an example regarding steady state and fault conditions. Finally, the influence of various parameters upon such interferences is discussed. The paper provides an insight on how to control the generated electromagnetic interference in the dc line on account of the induced voltage from the neighboring ac line.