Effect of DC Filters on Selection of Fault Discriminator for Unit Protection of Monopolar HVDC Transmission System

Abstract

Various research works reported on the unit protection of monopolar high-voltage direct-current transmission system assumed either no dc filter or a certain type of dc filter in the system. From the survey of literature, it appears that no study has been made to evaluate the effect of the type of dc filter on the system performance and consequent effect on the selection of fault discriminator for development of protection schemes. The work reported in this paper aims at selection of suitable fault discriminators for unit protection of HVDC transmission system in the presence of three different types of dc filter. The study has been carried out on a 500-kV line- commutated-converter-based monopolar HVDC system equipped with any of the three filters, namely, cascaded double-tuned, parallel double-tuned or triple-tuned filter. Simulation has been carried out with PSCAD/EMTDC. Critical analysis of the simulation results shows how the type of the dc filter influences the choice of fault discriminator