Wind Tunnel Studies on the Galloping of Lightly-Iced Transmission Lines

Abstract

The aerodynamics involved in the galloping of lightly-iced transmission lines were studied in a series of wind tunnel experiments. A representative section of a lightly-iced conductor produced in an outdoor freezing rain simulator was used throughout. In the first set of experiments aerodynamic loads were measured on a static model at different wind speeds and angles of attack. These experiments showed that the well-established den Hartog criterion does not predict an instability at wind speeds associated with transmission line galloping. A second set of experiments examined the effects of different steady rotational motions on the aerodynamic loads. Automated controls were used to rotationally oscillate the model in a repeatable manner at various angles of attack and rotational amplitudes as well as frequencies. The drag remained consistent with quasi-steady values, while the lift was affected by the rotational motion. This rotation-induced lift was enhanced by ice surface irregularities, but further studies were needed to fully assess its importance.

Analysis of wind attack angle increments in wind tunnel tests for the aerodynamic coefficients of iced hangers

“…The former source of uncertainties can be reduced by improving the instrument equipment and the quality of the test. The wind tunnel test, as the common study method, has been widely used in the field of wind engineering research (An et al, 2016; Chabart and Lilien, 1998; Fleming and Popplewell, 2010; Guo et al, 2017; Keutgen and Lilien, 2000; Li et al, 2017; Loredo-Souza and Davenport, 2002), and the corresponding standard of wind tunnel test has been formulated. In addition, the performance and accuracy of equipments can meet the need of experiments.…”

“…Test model Variable range of wind angle attack (°) Wind attack angle increment (°) Li et al (2016) Iced cables 0 to 180 2 Fleming and Popplewell (2010) Lightly iced conductors 0 to 360 2 Chabart and Lilien (1998) Iced conductors -180 to 180 5 Lou et al (2014) Iced conductors 0 to 180 5 Cai et al (2015) Iced conductors 0 to 180 5 Yan et al 2014Iced conductors 0 to 180 5 Keutgen and Lilien (2000) Iced conductors 2180 to 180 5 Gjelstrup et al (2012) Iced bridge hangers 290 to 90 5 Yan et al 2013Iced conductors 2180 to 180 5 Liu et al (2013) Iced conductors 2180 to 180 5 Ma et al 2017Iced conductors 0 to 90 10 Chadha and Jaster (1975) Iced conductors 0 to 360 10 Demartino 2014Iced bridge hangers 0 to 180 10 Nigol and Buchan (1981) Iced conductors 280 to 80 20 2017Iced conductors 0 to 90 10 2 Chadha and Jaster (1975) Iced conductors 0 to 360 10 5 Nigol and Buchan (1981) Iced conductors 280 to 80 20 18…”

“…However, no subsequent analysis of the fitting equations was conducted. Fleming and Popplewell (2010) indicated that a reasonable approximation curve fitting could be achieved by considering intervals of 30°in analyzing the aerodynamic coefficients and Den Hartog coefficients of iced conductors. However, the analysis was performed based solely on wind attack angle increments of 2°.…”

“…The wind tunnel test is the primary measurement tool used in the field of wind engineering research and it plays a crucial role in structural wind engineering (An et al, 2016; Chabart and Lilien, 1998; Fleming and Popplewell, 2010; Guo et al, 2017; Hu et al, 2015; Keutgen and Lilien, 2000; Li et al, 2017; Loredo-Souza and Davenport, 2002). It has been found in the literature that wind attack angle increments may directly influence the accuracy of the test data in the wind tunnel tests of iced cable structures.…”

“…However, previous studies have not defined the specific wind attack angle increments, and different scholars have adopted nonidentical values. As shown in Table 1, different wind attack angle increments, such as 2° (Fleming and Popplewell, 2010; Li et al, 2016), 5° (Cai et al, 2015; Chabart and Lilien, 1998; Gjelstrup et al, 2012; Keutgen and Lilien, 2000; Liu et al, 2013; Lou et al, 2014; Yan et al, 2013, 2014), 10° (Chadha and Jaster, 1975; Demartino, 2014; Ma et al, 2017), and 20° (Nigol and Buchan, 1981), have been adopted in existing research while performing wind tunnel tests for the aerodynamic coefficients of iced cable structures. Therefore, selecting appropriate wind attack angle increments that can ensure the accuracy of the test data, shorten the period of experiment, and reduce the expense of the experiment is a problem that should be addressed immediately.…”