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Yongqing Liu
Fuzhou University

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The Research of Digital Algorithm Based on Frequency-Dependent Transmission Lines Yongqing Liu; Baina He; Yunwei Zhao; Hengxu Ha; Xinhui Zhang
Indonesian Journal of Electrical Engineering and Computer Science Vol 11, No 5: May 2013
Publisher : Institute of Advanced Engineering and Science

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Abstract

The algorithm for obtaining the discrete response of popagation function for frequency dependent parameter line is presented. Consider a minimum sampling period Tsm, that is, the highest frequency fH=1/(2Tsm) in the signal is taken into account. The impedance z(w) and the admittance y(w) are obtained in the frequency range of [0,fH] by employing the Carson’s formula. The propagation function at each frequency point is subsequently obtained, the impulse response in discrete time domain is then obtained using Poision Sum Formula. In order to avoid the long length of impulse reponse under the higher sampling frequency, the poles and zeros of z transform of discrete propagation function are evaluated by the Prony’s method. Subsequently, the coeffcients of the discrete infinite impulse response of propagation function are obtained. Using these coefficients the wave transfer sources can be easily computed by discrete convolution operation. The simulation tests show that the results using the propsed method is accurate, the error is not more than 1% in contrast of the results generated by EMTP. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2491
Study on Reactance Relays for Single Phase to Earth Fault on EHV Transmission Lines Yongqing Liu
Indonesian Journal of Electrical Engineering and Computer Science Vol 11, No 7: July 2013
Publisher : Institute of Advanced Engineering and Science

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Two questions about zero-sequence-reactance relay to overcome the disadvantages of high fault resistance for single phase to earth fault of high voltage transmission lines are discussed in this paper. The first question is about the phase difference between the measured zero-sequence current and voltage at fault position for un-balanced transmission lines. The second question is about the “in-phase” problem in reactance relays (or fault component reactance relays). This paper analyzes the two questions theoretically and the reactance relay is improved by a new discriminative principle. The capability against the fault resistance is largely enhanced by the improved schemes. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2835 
Co-Authors Baina He Hengxu Ha Xinhui Zhang Yunwei Zhao