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Author: search.filters.author.Chiradeja, PathomthatSubject: search.filters.subject.power system transients

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    Behaviour analysis of H-bridge high-voltage capacitor banks fault on 230-kV substation using discrete wavelet transform
    (2023-11-01)
    Chiradeja, Pathomthat
    ;
    Lertwanitrot, Praikanok
    ;
    Ngaopitakkul, Atthapol
    ;
    Pothisarn, Chaichan
    The protection of traditional high-voltage capacitor banks relies on an unbalance relay which operates when an internal fuse is blown. However, the unbalance relay cannot indicate the cause of the fault. Thus, an operator wastes time and human resources investigating the fault issues. In this paper, a fault which occurred in a 230-kV power system of Electricity Generating Authority of Thailand was observed by performing simulations using the Power Systems Computer Aided Design (PSCAD) program. The study system based on the double bus station and 72 MVAR capacitor banks was installed in the form of a back-to-back topology. Three scenarios were considered: normal condition, fault occurrence in one capacitor bank and fault occurrence in both capacitor banks. Current characteristics such as the current phase and difference in unbalance current were considered. In addition, discrete wavelet transform was applied to solve the ambiguity of current generated from the PSCAD. The authors’ results suggest that identifying fault events using a coefficient of wavelet is more efficient than relying on the current amplitude. The findings mentioned in this paper can be applied in a traditional power system protection scheme to enhance a system's reliability.
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    Identify Direct Lightning Strike Location Based on Discrete Wavelet Transform for 115-kV Transmission System
    (2022-01-01)
    Chiradeja, Pathomthat
    ;
    Ngaopitakkul, Atthapol
    This paper proposes three techniques for locating lightning strikes in a 115 kV transmission system over 88.5 km, based on the arrival time of a transient wave obtained from a discrete wavelet transform (DWT). The first technique calculates the location based on the 'type D' travelling wave method. The second technique analyses the first arrival time and same reflected-back wave arrival time between two substations. In the third technique, two sensors are installed to record arrival times at each sensor. Case studies of direct lightning strikes to phase conductors (shielding failure) are simulated using the 'Alternative Transients Program/Electromagnetic Transients Program' (ATP/EMTP). The influences of three parameters are considered: inception angles, the phase of the conductor, and the position at which the lightning struck the transmission system. By performing an operation scheme for all techniques, a positive sequence current is calculated, using a three-phase current from the ATP/EMTP program which is converted using Clark's transform. A positive sequence current is extracted to several scales using the DWT, and the orders of arrival times for both substations are determined. After the arrival times are obtained, each technique uses a different order of arrival time for calculating the lightning location. By comparing the average error among the three techniques, it is shown that the arrival time of the two sensors' technique is less than that of the other techniques.
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    Analyzing the Characteristics of Faults in a Transmission Line and High Voltage Capacitor Banks in a 115-kV-Power System Using Discrete Wavelet Transform
    (2022-01-01)
    Chiradeja, Pathomthat
    ;
    Ngaopitakkul, Atthapol
    The protection of conventional high voltage capacitor banks relies on an unbalance relay. However, investigating the faults requires time and human resources. To address this issue, the characteristics of system parameters were analysed in this study by performing simulations using the power systems computer-aided design software. The simulations were modelled based on a 115-kV-system of the Electricity Generating Authority of Thailand. The case studies involved faults in the transmission line, a single capacitor bank, and a back-to-back connected capacitor bank. Additionally, the influence of other factors on the system parameters was investigated, including the varying fault phase, location, and inception angles. Moreover, the discrete wavelet transform (DWT) was applied to analyse the system parameters comprehensively. The results indicate that the characteristics of system parameters in the case of faults occurring in a transmission line are unique when compared to those in the case of faults occurring in a capacitor bank. Furthermore, the discrepancy between the system parameters in the case of faults occurring in a single capacitor bank and two capacitor banks connected in a back-to-back topology was solved by applying DWT. Therefore, the study findings can aid in improving the efficiency of power systems and ensure their protection.