Journal Articles

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884

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Author: search.filters.author.Vittal, K.P.Subject: search.filters.subject.Electric fault currents

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    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.
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    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.
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    Superimposed current based differential protection scheme for AC microgrid feeders
    (Elsevier Ltd, 2023) Joshua, A.M.; Vittal, K.P.
    Legacy protection schemes face numerous challenges with the emergence of microgrids. Due to the complex controls, the fault responses in microgrids differ from conventional behaviour and vary with the operation mode. In this paper, a differential protection scheme based on fundamental frequency superimposed current phasors is proposed for microgrid feeders. The phasors are extracted using dq components instead of conventional Fourier algorithms. The performance of proposed method is tested for different fault scenarios by carrying out simulations in MATLAB/SIMULINK software. The results confirm that internal faults are detected in a few milliseconds. At the same time, the scheme remains insensitive to external faults with CT saturation and other system disturbances. The proposed scheme is unaffected by the microgrid mode of operation, direction of power flow and DG type. © 2023 Elsevier Ltd