For the protective relaying of UHVDC transmission line

this paper analyzes the problems existing in thetechnology and principle of protective relaying in practical engineering applications at home and abroad.Travelingwave protection as the main protection of the existing UHVDC line is obvious

but there is limited resistance to thetransition resistance

the sampling frequency requirements of higher. Differential under voltage protection

which isa redundant protection of traveling wave protection

is similar to the traveling wave protection

and the lack of the ba-sis of the whole set. Low voltage protection is strong in resistance to transition resistance

but its selectivity is poor

the action speed is not fast enough.The current differential protection has good selectivity

but it is influenced by theline distribution capacitance and the action time is long. In this paper

through the analysis of the UHVDC transmis-sion line protective relaying technology progress and the existing problems

the prospect of applying boundary element

characteristic frequency

control and protection

with further research ideas and technology have been put forward.