Wave propagation characteristics and computation improvements for transients on finite-length overhead lines
Loading...
Files
Date
2020-11-19
Authors
Shi, Xi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This thesis first describes the derivation of the impedance and admittance of an infinitely long conductor line and a finite-length conductor line over the earth with finite resistivity. Then, the impedance, admittance, propagation constant (attenuation and velocity), and characteristic impedance of the finite-length and infinitely long conductors are compared, which has not been comprehensively reported in earlier literature. It is shown that the impedance of a finite-length conductor is always smaller than the PUL impedance and converges to the PUL impedance as the conductor length increases. The converging length, i.e. the applicable length of the PUL parameters, becomes smaller when the frequency is higher. The admittance of the finite-length conductor is greater than that of the PUL admittance. The attenuation constant is smaller and the propagation velocity is greater in the finite-length conductor. The characteristic impedance shows a similar trend to the impedance.
To further investigate transient responses, an exponential Fourier transform method is adopted to evaluate the time domain responses from frequency domain formulae. The linear midpoint interpolation method is proposed to alleviate the Gibbs oscillation. By applying the weighting order, better results can be obtained in terms of Gibbs oscillation suppression. The Fast Fourier Transform (FFT) and inverse Fast Fourier Transform (IFFT) technique are also adopted to solve transmission line transients problems, and this technique can further improve efficiency.
By applying the above explained approaches, the transient responses are calculated. The calculated results show that the difference is very small when the line length is large, regardless of the external power grid structure and parameters. When the length is short, the switching surges on a finite-length conductor are significantly different from those calculated by the conventional PUL approach. The difference between the finite-length and PUL parameters is less noticeable in a fault surge when the source impedance and/or fault impedance is large.
Description
Keywords
Finite-length conductor, PUL parameter, Overhead line, Transient, Fourier transform
Citation
X. Shi, A. Ametani, A. Gole and J. De Silva, “Influence of a Finite-length Overhead Conductor on Wave Propagation”, IEEJ High-Voltage Conference, Paper HV-20-x2, January 2020.
X. Shi, A. Ametani, A. Gole and J. De Silva, “Influence of Finite-Length Overhead Conductors on Wave Propagation Characteristics and Transients”, 2020 IEEE Power and Energy Society General Meeting, Montreal, QC, Canada, 2020
X. Shi, A. Ametani, A. Gole and J. De Silva, “Influence of Finite-Length Overhead Conductors on Wave Propagation Characteristics and Transients”, 2020 IEEE Power and Energy Society General Meeting, Montreal, QC, Canada, 2020