Study On Aerodynamic Characteristics And Wind-induced Swing Of Transmission Lines

Terrain and climate conditions of the region which transmission lines go through are complex,wind-induced conductor vibration caused by wind load deserves attention,especially flashover accidents caused by wind-induced conductor swing.Researches on aerodynamic characteristics of bare and iced conductors and calculation models and methods of conductor swing were carried out.Rigid models which imitate the surface roughness of real conductors accurately are manufactured,wind tunnel tests of single conductors and two,four and eight bundled conductors are carried on,analysis is focused on the influence of the Reynolds number and wind attack angles on sub-conductors,and the results are compared with some existed ones at home and abroad.The influence of the Reynolds number on sub-conductors is different from that on single conductors;trial values of drag coefficients are smaller than code values due to the effect of wake interference caused by mutual shielding of sub-conductors,and such effect is weakened with the increase of turbulence,but still can't be ignored.Wind tunnel tests of typical D-shaped and crescent-shaped single conductors and eight-bundled conductors are carried on,the influence of wind velocity on D-shaped single conductor aerodynamic characteristics is analyzed,research is focused on the changing patterns of aerodynamic coefficients of iced eight-bundled sub-conductors,and the results are compared with some existed ones at home and abroad.The aerodynamic characteristics of D-shaped single conductors are almost the same within the wind velocity range from 7 m/s to 13 m/s;compared with single conductors,eight-bundled sub-conductor drag coefficients change more obviously with wind attack angles;an expected peak of the curve which represents the lift coefficients under different wind attack angle doesn't appear,which may be related to ice shapes and surface roughness.Average wind field around a typical single mountain is simulated by CFD;multi-span models of transmission lines which are parallel to the ridge are established,static conductor swing under the combined effect of horizontal and vertical wind velocity is calculated,and the influence of rising air flow on conductor swing is analyzed.On the mountainside of an upwind slope,large vertical wind velocity emerges as the result of the climbing effect and horizontal wind velocity decreases due to the blocking effect,when calculating the conductor swing of transmission lines along the mountainside,the difference from flat terrain wind field should be considered;the conductor swing of transmission lines along the ridge on the mountaintop is large and changes a little with height.3-D fluctuating wind velocity of flat terrain is simulated by the POD method;multi-span models of transmission lines in flat terrain are established,wind load which follows the change of wind attack angles is accurately calculated,using the conductor aerodynamic coefficients by wind tunnel tests,dynamic conductor swing is calculated in time-domain,the influence of vertical fluctuating wind velocity and friction at the joint connecting suspension insulator strings with cross arms on conductor swing is analyzed.When calculating the conductor swing,single-conductor models with fixed aerodynamic coefficients are suggested to be used for bare conductors,while multi-bundled models with changing aerodynamic coefficients under different wind attack angle are suggested to be used for iced conductors.