Study On Caculation Of Conductor Swinging Under Fluctuating Wind Loads

In our country, the phenomenon of imbalanced power resources is serious. As the major power transfer method, Transmission system develops dramatically, but it is severely threatened by flashover accidents which were caused by conductor swinging. Therefore, the research on accurate and efficient computation methods of the displacement of insulator has great practical significance in engineering.Considered the relative velocity of conductor and wind, a method to calculate conductor swinging that affected by aerodynamic damping was established. Then the time-depending fluctuating wind loads would act on transmission line were simulated with the combination of harmonic wave superstition method and quasi-steady assumption. A nonlinear dynamic transmission line model which was consisted of eight-span electrical conductors was established precisely by using finite element method. Furthermore, the impact of aerodynamic damping caused by conductor movements on dynamic response of the transmission line was discussed in detail. It is shown that the aerodynamic damping can reduce the maximum value of conductor swinging significantly, when calculate displacement of insulator by dynamic analysis must take the aerodynamic damping into concern. On the other hand, the aerodynamic damping gained with the US transmission line design code ASCE No.74 was adopted to compute the displacement of insulator. The result of two methods to calculate the response of insulator under aerodynamic damping were compared. It shows that:the results are close to each other, aerodynamic damping gained with ASCE No.74 can be used in future research.Compared the difference between Multi-span modal and single pendulum modal, investigate the accuracy of single pendulum modal. Through discussed the difference between maximal value and the mean value of conductor swinging calculation results, this thesis researched the impact of turbulent wind velocity on the wind-induced dynamic amplification effect. In order to have a better understanding of wind load calculation in the computation of conductor swinging, the setting of calculation parameters were compared among four different National design codes:?GB 50545???ASCE No.74???IEC 60826-2003? and?BS 8100? Furthermore, based on a real eight-span transmission line, the differences among the calculation results of different codes were analyzed under the same design condition. The result shown that: using the single pendulum modal to calculate the rotation angle of suspension insulator string is safe; The dynamic magnification factor is about 1.3?1.5;wind load defined in Chinese design code is the smallest, the main cause lies in the less of comprehensive consideration of wind pressure asymmetrical coefficient and dynamic magnification factor.A frequency-domain analysis method of conductor swinging is presented in this paper. Geometric nonlinearity is considered when the mean wind load acting on the wires, A single-span transmission line was taken as the research modal, Moreover, In order to improve calculation efficiency, twenty?ten?five?three?two mode vibration was superposed. The result shown that:The response of conductor swing in the frequency domain and in time domain is close to each other, the frequency-domain analysis method has proved to be feasible; Taking the first and second model for SRSS combination, a high Precision conductor response can be got with the best calculation efficiency.This thesis presents the frequency domain character of insulator Strings swing, found out that wind dynamic response predominantly background, and the resonance can be ignored. Load-Response-Correlation (LRC) method was adopted to calculate the equivalent static wind load (ESWL) of a single-span transmission line, the response of the single-span transmission line that acted ESWL or the time-depending fluctuating wind loads were compared. The result shown that:The ESWL of conductor that based on the LRC method is precisely.