Study On Aeolian Vibration And Subspan Oscillation Of Bundle Conductor

With the rapid growth of electricity transmission capacity, the adoption of bundle conductor, high-capacity and long-distance transmission lines have become inevitable. Aeolian vibration and subspan oscillation can easily cause damage of the bundle conductor and electric power fittings, which have a serious threat to the safe and reliable operation of transmission lines. As an important lifeline facility, the damage of transmission line system can lead to the paralysis of power supply system and cause huge economic losses and other secondary disasters. However, the existing methods are difficult to meet the design requirements. In order to ensure the safe operation of transmission line system, it is necessary to make further research in this field.In this dissertation, the numerical simulation on bundle conductor in a cross-flow is implemented by using computational fluid dynamic (CFD) method to study the aeolian vibration mechanism, wind power input, and the average aerodynamic characteristics of bundle conductor. The calculation precision of bundle conductor's aeolian vibration is improved through the modified study of energy balance pricinple. The conductor vibration test is adopted to study the energy dissipation characteristics of stockbridge damper, wire damper, spacer damper. Using the numerical simulation results of average aerodynamic characteristics of bundle conductor and combined with stability theory, nonlinear oscillation theory and nonlinear finite element method, the mechanism of subspan oscillation is studied and the calculation methods are presented. The specific contents are as follows:(1) Firstly, CFD numerical simulation of the flow around the fixed single conductor and bundle conductor is carried out to verify the reliability of solution method. The three-dimensional effect is also considered. By means of the dynamic mesh method, the aeolian vibration mechanism and properties of single conductor and bundle conductor are studied. Moreover, the differences of the two cases are analysised and discussed. The wind power input of single conductor is numerically obtained through the simulation of the flow around a vibrating conductor. The numerical value of wind power input has a good agreement with the experimental value by the researches in wind tunnel tests. It's confirmed that the numerical method is feasible. The subconductors of the bundle conductor are also obtained throuth the CFD numerical simulation. Meanwhile, the influences of subconductor horizontal spacing, inclination angle, turbulence intensity were discussed. And the analytical expressions of wind power input for bundle conductor are gained through the curve-fitting of numerical results. This can provide a basis for the solving the aeolian vibration response of bundle conductor.(2) According to IEEE standards, the vibration test of single and bundle conductor are designed and carried out. Through the single conductor test, the self-damping characteristic of conductor and the anti-vibration property of stockbridge dampers are investigated. Based on the theory of wave propagation, the calculation method for the energy dissipation of stockbridge damper, considering the damper's installation posisiton, is established. And the method is validated by the corresponding vibration test. The vibration characteristic of the bundle conductor and the energy dissipation characteristics of spacer damper, wire damper, stockbridge damper are studied through the bundle conductor vibration test.(3) The modified energy balanced method is established to analysis the aeolian vibration of bundle conductor, which is different from the traditional reduction factor method. The transfer matrix method is used to calculate the vibration frequency and mode of the bundle conductor. Combined with the wind power input of bundle conductor by means of CFD simulation and the energy dissipation calculation method for conductor self-damping and stockbridge damper, the modified energy balanced method is established to calculate the response of the aeolian vibration of bundle conductor. Compared with the reduction factor, the modified energy balanced method is more reasonable and effective.(4) The average aerodynamic characteristics of bundle conductor is obtained by the CFD numerical simulation. Moreover, the influences of the conductor spacing, turbulence intensity, Reynold number effect are discussed. On the basis of the quasi-static aerodynamic theory, the oscillator models of two-degree-of-freedom motion and four-degree-of-freedom motion are built. Through the instability analysis of the two oscillator models, the critical conditions for the occurrence of subspan oscillation are investigated. By means of numerical solution and the average method, the dynamic response of subspan oscillation is calculated. Meanwhile, the investigation is made to study the influence of wind velocity, the damp of bundle conductor system, the frequency ratio on the subspan oscillation. The results of the two oscillator models are compared and analysed to discuss the influence of the windward's oscillation freedom.(5) The finite element model of bundle for subspan oscillation analysis is established. In addition, the aerodynamic coefficients of bundle conductor with different conductor spacing and inclination angle are obtained through computational fluid dynamics method. The Newton-Raphson iteration method is employed to determine the initial configuration of the bundle conductor and the Runge-Kutta method is applied to carry out nonlinear numerical simulation. Through that, the subspan oscillation response is obtained. Finally, the impact of conductor spacing, inclination angle and spacer arrangement on subspan oscillation are investigated with the FEM simulation.The studies of aeolian vibration and subspan oscillation of bundle conductor have important theoretical significance and economic value. This dissertation provides an effective theoretical basis and reasonable references for the anti-vibration design and further study of the two kinds of wind-induced vibration.