Faculty Publications
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Item Design and simulation of quadrilateral relays in ac transmission lines with vsc-based hvdc systems under phase-to-ground fault condition(Politechnica University of Bucharest Splaiul Independentei 313 - Sector 6 Bucharest 77206, 2019) Muniappan, M.; Vittal, K.P.Voltage source converters (VSC)-based high voltage direct current (HVDC) transmission system can be used to integrate the offshore wind power generation with an AC grid. Due to the interconnection of VSC-HVDC system with the AC grid, an operation of distance relays might get affected. Also, fault resistance plays a significant role in the performance of ground relays. The ground faults have higher fault resistance causes the accuracy of the ground relay gets affected significantly. In this paper, the three-zone quadrilateral characteristic-based distance relay is designed to protect the AC transmission lines under phase-to-ground fault with fault resistance. Simulation studies are carried out to test the performance of the quadrilateral relay under phase-to-ground fault including various fault resistance cases in an AC transmission line with the effect of VSC-HVDC system. The impact of the dynamic conditions of the VSC-HVDC system on the performance of the quadrilateral relays under phase-to-ground fault with fault resistance cases is presented. Also, the performance comparison of the quadrilateral relay with the mho relay under such conditions is presented. © 2019, Politechnica University of Bucharest. All rights reserved.Item Performance Evaluation of Distance Relay in the Presence of Voltage Source Converters-Based HVDC Systems(Korean Institute of Electrical Engineers elecjour@kiee.or.kr, 2019) Muniappan, M.; Vittal, K.P.Voltage source converters (VSC)-based high voltage direct current (HVDC) link is an economical option for the long distance bulk power transmission, and it can be used to interconnect the offshore wind farms with an AC grid. Due to the penetration of VSC-HVDC system into the AC grid, the performance of the distance relay gets affected when a transmission line close to the point of common coupling (PCC) subjected to power system disturbances. In such condition, the PCC voltage is increased due to the VSC-HVDC control action, that causes the Zone-2 fault can be seen as a Zone-3 fault. As a result, the miscoordination of Zone-2 protection can occur in the distance relays. This paper presents both the analytical and simulation studies carried out on a VSC-HVDC system influence on the distance relay performance under fault conditions using PSCAD/EMTDC. Simulation results show that the presence of VSC-HVDC system greatly affects the performance of the Zone-2 and Zone-3 relay in an AC transmission line. Besides, the maloperation of the Zone-2 and Zone-3 relay is mitigated by varying the AC voltage reference input of the decoupled d-q controller of VSC-HVDC. Also, the effect of fault resistance on Zone-1 ground relay performance is analyzed. © 2019, The Korean Institute of Electrical Engineers.Item DC Fault Protection in Multi-terminal VSC-Based HVDC Transmission Systems with Current Limiting Reactors(Korean Institute of Electrical Engineers, 2019) Muniappan, M.; Vittal, K.P.Multi-terminal VSC-based HVDC transmission system is the recent interest for grid integration of large-scale offshore wind farms. Protection of multi-terminal voltage source converters (VSC)-based HVDC transmission systems against DC faults is challenging. This paper presents a single-ended protection scheme for DC faults in a three-terminal VSC-HVDC transmission system. The under-voltage criterion is used to distinguish the DC faults from the transient and normal conditions. The rate of change of DC voltage and current as well as the variation of transient energy is used to discriminate the internal faults from the external faults. The DC fault current has very high value within a few milliseconds during the transient phases such as the capacitor discharging and diode freewheeling stages. Therefore, current limiting reactors are introduced in series with the DC circuit breaker to maintain the DC fault current within the breaker capacity. The single-ended protection scheme is tested with the three-terminal VSC-HVDC transmission system with current limiting reactors for various DC fault conditions. The DC fault data is generated from PSCAD/EMTDC simulation and the protection scheme is tested in MATLAB environment. Test results show that the proposed protection scheme gives reliable protection for the DC faults in a three-terminal VSC-HVDC transmission system. © 2019, The Korean Institute of Electrical Engineers.