Based on the boundary characteristic of a dc transmission

line, the response of transient harmonic current in the

line-commutated converter HVDC transmission system is analyzed

under various fault conditions in this paper. A new transient

harmonic current protection scheme is proposed. The discrete

Fourier transform is used to extract transient harmonic currents

at both terminals of the dc transmission line and the type of fault

can be identified by the transient harmonic currents. Two main

factors including fault resistance and fault location that affect

performance of the protection are also discussed in this study. The

test system is modeled based on the CIGRE benchmark including

distributed parameters of the dc transmission line. Comprehensive

test studies show that the performance of the transient harmonic

current protection scheme is encouraging. It can not only identify

internal faults and external faults correctly and quickly, but also

can respond to high ground resistance faults.