Stability evaluation and aerodynamic damping study on three-degree-of-freedom coupled galloping of iced conductors
Lou Wenjuan1 Yu Jiang1 Jiang Xiong1 Lu Ming2 Lü Zhongbin2
1. Institute of Structural Engineering, Zhejiang University, Hangzhou 310058, China;
2. Henan Electric Power Testing and Research Institute, Zhengzhou 450002, China
Abstract： Wind tunnel tests for galloping of an ice-coated D-shape sectional model of 6-bundled conductors were carried out using a scaffolding spring suspension device with adjustable 3-DOF frequency. By adjusting the ratio of vertical to torsional natural frequency of vibration and the wind speed under different attack angles, unstable vertical galloping, torsional galloping, vertical-torsional coupled galloping and torsional-horizontal coupled galloping were excited and recorded, respectively in the wind tunnel tests. Vertical and torsional aerodynamic damping identified from galloping of measured response and numerical simulation was compared with the calculation value based on Den Hartog or Nigol theory. The corresponding influence of aerodynamic characteristic, natural vibration characteristic and wind speed on aerodynamic damping had been studied separately. Results from the wind tunnel tests indicate that the absolute value of conductor’s negative aerodynamic damping may increase exponentially with wind speed increasing, or that it may first increase and then decrease to less than the structural damping because of the difference in positive and negative of Den Hartog coefficient or Nigol coefficient and the difference in the ratio of vertical to torsional frequency. It also indicates that galloping theory of single-degree-of-freedom can’t predict three-degree-of-freedom coupled galloping. Conditional stability criterion for three-degree-of-freedom coupled galloping of iced conductor was proposed based on eigenvalue perturbation method. The proposed stability criterion can explain the galloping phenomena which can’t be explained by Den Hartog or Nigol theory of single-degree-of-freedom. The conclusion was verified by test results.
