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Author: search.filters.author.Yutthagowith, P.Subject: search.filters.subject.Equivalent circuit

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    A modified pi-shaped circuit-based model of grounding electrodes
    (2016-12-19)
    Yutthagowith, P.
    This paper proposes a modified pi-shaped circuitbased model of grounding electrodes. The validity length and soil resistivity of the proposed model are from 2 m to 40 m and from 50 m to 2000 m, respectively. The equivalent circuits in the form of pi configuration are modeled by lumped parameters composing of inductance, resistances, and capacitances. The voltage responses to the standard lightning currents of grounding electrodes either calculated by an electromagnetic model or from experiments are matched with those of the proposed model. A curve fitting technique is employed to extract parameters of the equivalent circuit. The satisfactory agreements have been observed. The simple soil ionization model can readily be adapted in the proposed model. The proposed model is very useful in implementation with a circuit simulator such as EMTP, Pspice, and so on. The proposed circuit model can be adapted for being the models for development and design of the grounding system for lightning protection system in transmission and distribution systems in an effective way.
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    Internal failure analysis of transformer windings
    (2012-12-31)
    Tuethong, P.
    ;
    Yutthagowith, P.
    ;
    Kunakorn, A.
    ;
    Potivejkul, S.
    This paper presents internal failure analysis of transformer windings based on the characteristic of winding impedance in the frequency domain. Two winding samples are selected to test. The simple equivalent circuit of the transformer winding is investigated and proposed. The two windings under test have 76 turns with different length. An iron core is either inserted or not inserted inside a winding in the test to investigate the effect of the iron core. Turn to turn short circuit on the windings is considered as internal failure in this paper. The simulated turn to turn short on the model is carried out in the experiment to observe impedance characteristic in the frequency domain. A number and position of short turns are varied to observe characteristics of impedances The impedance of the models of the transformer windings are measured by a spectrum analyzer in a wide frequency range upto 2 MHz. From the test results, it is investigated that a resonance frequency of the transformer model is depended on a number and position of short turns. From the investigation, it has high possibility that the characteristic can be used for analysis of internal failures occurring in a transformer. © 2012 IEEE.