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
Highlights
High-voltage direct-current (HVDC) transmission systems are widely used for interconnection of far-away load centers due to their both high efficiency and competitive costs [1,2]
A monopolar LCC-HVDC system has been simulated with three different dc filters using PSCADTM/EMTDCTM
Responses of the system to solid faults occurring at three internal locations and two external locations have been analyzed for three system variables, namely, incremental current, incremental power and transient energy
Summary
High-voltage direct-current (HVDC) transmission systems are widely used for interconnection of far-away load centers due to their both high efficiency and competitive costs [1,2]. Reference [9] proposed a unit protection scheme with transient energy as the fault discriminator and no dc filter was considered This technique shows a reduction in sensitivity with increase in fault resistance. Reference [10] proposed an algorithm with transient harmonic current as fault discriminator and the filter considered was cascaded double-tuned type, the limitation of which was again reduction in the sensitivity with increase in fault resistance. Reference [14] puts forward a protection scheme using differential current as the fault discriminator while the dc filter considered was triple-tuned type. It shows an improved performance over the conventional differential current protection in terms of sensitivity, it is applicable only for back-up protection as stated by the authors. The configuration and component values of cascaded double-tuned filter assumed were the same as given in [12] and those of the remaining two types of dc filters are given in Appendix
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