Power transmission lines transient electromagnetic fields-a study of scale modeling and the effects of ground loss
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Date
2012-04-09
Authors
Gharagozloo, Pooya
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Abstract
In this thesis, the problem of calculating power transmission line induced or radiated
electromagnetic fíelds is studied by decomposing the line into a large number of snall
segments, k¡own as Hertzian dipoles. Since the presence of lossy ground makes the
electromagnetic fìeld distribution very different from that of the same dipole over
perfectly conducting ground, different approaches should be followed for the lossy and
lossless ground assumptions. The contribution of each dipole on the total electric and
magnetic field is calculated using three analytical techniques. Two of these methods are
frequency-domain solutions for the problem of dipole radiation above lossy ground,
while the third method is a time-domain exact solution for the same problem based on the
assumption of perfectly conducting ground. The theoretical background and extent of
validity of each technique are reviewed in this thesis. Tlie results derived by applying
each method are compared with those obtained using a commercial software package.
The time-domain solution for the problem of power transmission line electromagnetic
fields is obtained using Fourier and inverse Fourier transforms, rvhich enables us to
obtain the electromagnetic waveforms associated with power system transients. The
effect of different parameters such as conductivity and relative permittivity of the ground,
the line{o-observation point distance, height, and sag of the transmission line is studied.
Further, the impact of downscaling of transmission line on different electromagnetic
parameters is analyzed, and the appropriate scale factor for each parameter is derived.
Description
Keywords
power, transmission, electromagnetic, fields