Aerodynamic modeling for large-amplitude galloping of four-bundled conductors

The galloping of overhead transmission lines, which is characterized by large-amplitude, low-frequency oscillations, occasionally occurs when the lines are subjected to ice and snow accretion. To evaluate the applicability of an aerodynamic force model based on the quasi-steady theory for simulating the galloping of overhead transmission lines, aeroelastic tests were performed in a wind tunnel using a rigid-body section model of four-bundled conductors. First, large-amplitude, low-frequency galloping was successfully simulated in a wind tunnel test using a unique support technique proposed in this paper in the vertical, horizontal, and torsional directions. Then, two different formulations of quasi-steady aerodynamic forces affecting four-bundled conductors were presented: one formulation considers all conductors as one group, whereas the other considers each subconductor independently. The two formulations are evidently different in that the aerodynamic forces attributable to torsional velocity can only be derived using the second formulation. Finally, the response amplitudes obtained from the wind tunnel tests and time-history response analyses were compared, and the results suggested that, to simulate large-amplitude, low-frequency galloping, quasi-steady aerodynamic forces should be formulated, not for all conductors together as one group, but for each subconductor independently.