Lessons learned from testing of a transmission line model at the WindEEE dome under simulated downbursts

Abstract eng:
The repeated failure incidents of lattice transmission line structures during downburst events motivated the authors to conduct a large-scale testing program at the WindEEE dome, at The University of Western Ontario. An aero-elastic model of a multi-span transmission line is designed and tested in order to asses the behaviour, determine the critical downburst configurations, and quantify the dynamic response of the line due to downburst induced loads. The downburst wind field is simulated at WindEEE as an impinging jet with a diameter-to-height ratio (H/D) of 1.2. Such a ratio allows the formation of the downburst main ring vortex. Many variables are considered in the testing program including different line spans, downburst wind speeds, number of spans, and downburst locations relative to the line. The considered line consists of V-shaped guyed towers supported by pin supports at the base and four guys at an upper level of the towers. The time history response of various measured quantities is decomposed into mean, background and resonant components. The analysis of the test results allows identification of the critical downburst configurations leading to peak responses at various locations of the line. The load sharing between the guys and the main body of the tower is determined for each configuration as well as the ratio between the longitudinal and the transverse conductor forces transferred to the tower. Finally, the test results allow quantifying the contribution of the resonant response to the peak response at various locations of the tower and for each downburst configuration. The main findings as well as the lessons learned from this testing program are presented in this paper. Introduction Recent reports highlighted that downbursts are one of the major causes of the failure of transmission line systems pertaining weather-related events. Among those failures are the chain failures of 23 towers in South Australia during a series of downburst events that occurred in September 2016 [1]. Similar incident occurred in China where more than 50 towers failed during downburst and tornado events [2]. In Ontario, Canada, two towers serving two different lines in the same area failed during a microburst event in 2006 [3]. McCarthy and Melsness [4] reported a chain of transmission line failures near Winnipeg, Canada during a series of downburst events. Generally, the failed towers were

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