Response of monopolar HVDC system in presence of single double-tuned dc filter

Study of the response of an HVDC system to various conditions, types and locations of fault on the system is basic to developing suitable protection techniques and algorithms. This paper presents a study of the behaviour of monopolar HVDC system in the presence of a single double-tuned dc filter. CIGRE Benchmark model for monopolar HVDC system has been simulated on PSCAD/EMTDC for the study. Five different fault locations, viz. three dc line faults (two faults near the line ends and the third fault at the middle point of the line) and two ac side faults (one near the rectifier and the other near the inverter), and five different values of fault resistance (ranging from 0 to 2000 ohms) have been considered. It has been observed that incremental current and incremental power in the HVDC line can discriminate only mid-line dc faults from ac fault. Also, incremental current can discriminate between rectifier-side ac fault and inverter-side ac fault for all values of fault resistance, whereas incremental power can do so only for lower values of fault resistance (0 ohm and 10 ohms). Transient energy can discriminate dc line faults at all locations from ac faults with all values of fault resistance. However, transient energy can discriminate rectifier-side ac fault from inverter-side ac fault only for low values of fault resistance (0 ohm and 10 ohms) and not for high values. This study can be very effectively used in developing a protection algorithm/technique. The study can be further extended to analyze the performance of HVDC system in the presence of any type of the dc filter and for any length of the line. (paper)