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The effect of corona on wave propagation on transmission lines

University of British Columbia

Fast transients on power transmission systems, such as the ones produced by lightning and faults, are usually modelled by the Telegrapher’s Equations which, because of the corona effect, are nonlinear. Although it has been long recognized that the method of characteristics of partial differential equations (PDE’s) theory is the most adequate to tackle this problem, its previous applications have been very limited. A very general technique for the simulation of transients on lines with corona, based on the method of characteristics, is thus proposed in this thesis. This technique consists of representing the transmission lines by a system of first order quasilinear partial differential equations (PDEs) and of solving them on a characteristic system of coordinates by applying interpolation techniques. A method of analysis and simulation is first developed by applying the technique of characteristics with interpolations to the 2x2 system of quasilinear PDE’s representing a monophasic line with static corona. This method is further implemented on a computer. The numerical examples provided show that this method overcomes the problem of numerical oscillations which is often found at the tails of waves simulated by means of conventional methods based on constant discretization schemes. Another important feature of the developed method is that it requires substantially fewer discretization points than the conventional ones. The developed method is then extended to the time domain analysis of multiconductor lines both, the linear ones and the quasilinear ones with static corona. Most conventional methods for the analysis of multiconductor lines in the time domain are based, either directly or indirectly, on modal transformations from frequency domain analysis. One problem with this approach is, however, that these transformations usually introduce complex quantities which lack physical meaning in the time domain. The extension developed here maintains the analysis in the domain of the real numbers. In the case of transmission lines with corona, an additional problem of conventional modal transformations is that they presuppose linearity. The extension developed here avoids this shortcoming.

Thesis/Dissertation

application/pdf

2008-12-18

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http://hdl.handle.net/2429/3122

Electrical and Computer Engineering

University of British Columbia

UBCV

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