Research On Analytic Solution Of Galloping Of Iced Conductor Considering Geometric Nonlinearity And Environmental Factors And Time-delay Control

With the implementation of the power energy development strategy of “West-East Electricity Transmission Project” and "south-north electricity exchange ",a large number of UHV and UHV transmission lines have been constructed,which makes the safe operation of transmission lines even more important.Galloping is one of the most destructive factors to the safe operation of transmission lines,and it can cause tower collapse,line breaking,hardware damage and so on.In recent years,it still happens around the world.Therefore,it is significant for the safe operation of transmission lines to strengthen the research on galloping and its control.In this paper,the effects of geometric nonlinearity,thermal stress and turbulence on the galloping response were studied theoretically based on continuum model.The control effect of time delayed absorber on galloping was also investigated.The main works of this dissertation are as follows:Aiming at the problem that the effect of geometric nonlinearity on galloping cannot be considered in the general expression of galloping amplitude at present,the modified Lindstedt-Poincaré perturbation method was used to derive the analytical expression of galloping amplitude and frequency based on the continuum model of iced conductor,which can consider the evident geometric nonlinear.Then,the influence of quadratic nonlinearity and cubic nonlinearity caused by geometric nonlinearity on the amplitude and frequency of galloping was analyzed in detail for different wind speed,initial horizontal tension and span length by using the derived expression.Aiming at the important influence of the thermal stress on galloping of iced conductor,the Irvine suspension theory was extended to thermoelastic problem,and a continuum model was proposed to analyze the effect of thermal stress on galloping.The approximate analytical solutions of the amplitude and frequency of galloping were obtained by using the modified Lindstedt-Poincaré perturbation method.Then,the influence of thermal stress on the amplitude and frequency of galloping was studied for different wind speed,initial horizontal tension and span length by using the obtained analytical solution.Aming at the lack of theoretical research on the effect of turbulence on galloping in nonlinear vibration,the turbulence was introduced into continuum model by the method of equivalent parameter excitation,and the modified multi-scale perturbation method was used to solve it.Then,the influence of different excitation frequency and intensity on critical wind speed,amplitude and frequency of galloping were studied.Finally,aiming at the problem that the additional mass was too large for preventing galloping using Tuned Mass Damper,we improved it by using the time-delay mechanism.A vibration absorber with displacement time delay control was proposed.Based on the oscillator model of iced conductor and time-delay absorber,the analytical solution of onset wind velocity and galloping amplitude was derived by using normal form theory and harmonic balance method.Then,the galloping amplitude of the time-delay absorber was compared with that of the ordinary absorber by using the derived analytical expression.It was proved that the time-delay vibration absorber had better control effect on galloping than the ordinary vibration absorber.Moreover,the variation regularity of the galloping amplitude on the time delay parameter and gain factor of the system were analyzed in detail by using the obtained analytical expression.