Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Ashraf El Damatty

Abstract

Electricity is transmitted by Transmission Lines (TLs) from the source of production to the distribution system and then to the end consumers. Failure of a TL can lead to significant economic losses and to negative social consequences resulting from the interruption of power. High Intensity Winds (HIW), in the form of downbursts and tornadoes, are believed to be responsible for more than 80% of the weather-related failure of TLs around the world. The studies reported in this thesis are part of an ongoing extensive research program at Western University focusing on the response of TLs under HIW. Previous investigations conducted to study the behavior and to assess the failure of TLs under downburst wind indicated the importance of accounting for the forces transmitted from the conductors to the towers. The current thesis focuses on the response of TL conductors subjected to downburst wind while considering various terrain exposures. The thesis is written using the "Integrated Article" format and includes various complementary studies. First, an effective numerical technique to analyze transmission line (TL) conductors subjected to HIW events is developed. This is followed by a derivation of a simplified closed form solution to estimate the forces transmitted from the conductors to the towers due to downburst winds. Then, an expression for the conductor aerodynamic damping, which is a main parameter affecting the conductors’ dynamic behavior, corresponding to downburst wind, is derived and validated. Afterwards, dynamic behaviour of TL conductors under downburst and synoptic winds corresponding to open terrain exposure is investigated. In order to account for other terrain exposures, a new roughness model adequate for Large Eddy Simulation (LES) of moderate-rough to rough terrain exposures typically encountered by TLs is developed and validated. Then this model is used in conducting LES of downbursts for various terrain exposures in order to: (i) characterize the downburst turbulence, (ii) investigate the dynamic behavior of TL conductors under downburst wind corresponding to different exposures. The research accomplished in this thesis, in terms of development of efficient structural analysis tools and characterization of the wind field, provides an advancement in knowledge about the behavior of transmission lines in general and conductors in particular during downburst events.

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