The Dynamics Study Of Iced Bundle Conductors

The overhead transmission lines are often in galloping under the action of the icing, windand other loading. The power system can be damaged seriously by galloping, which is a kindof vibration with large amplitude and low frequency and lasts long. The purpose in this paperis to study the vibration characteristics of transmission lines by nonlinear dynamics theory,and to simulate the galloping process, investigate the effect of wind velocity, line structureand electric power fittings on galloping through building the finite element model oftransmission lines, meanwhile, a optimization approach for preventing galloping is proposed.According to the principles of elasticity mechanics, a continuum dynamics model of icedtransmission line galloping in plane can be established. By Galerkin method, a set of partialdifferential equations are transformed to a set of ordinary differential equations which aresolvable, and the vibration equation of one degree-of-freedom in plane is obtained by makingthe first modal truncation to this equation. The steady amplitude and its relationship withnonlinear transient inherent frequency are obtained by average method to solve the equationsof the first order approximate solutions. The effect of initial tension and galloping amplitudeof the transmission line on the natural frequency is investigated deeply, proposing therelationship between nonlinear natural frequency and galloping amplitude during galloping oficed transmission line. A qualitative analysis is made towards frequency shift in galloping oftransmission line.Based on the finite element model of iced bundle conductors made by 3D beam elementin this paper, the static form-finding and modal analysis have been conducted. At the sametime, the time history curve of galloping transmission line is obtained by programming thecomputational code of transmission line under the action of aerodynamic load withemployment of ANSYS parametric design language. Through the investigation of effect ofwind velocity and span on the amplitude of transmission line and its dynamic tension, theresult shows that the galloping amplitude of transmission line with the same span and itsdynamic tension increase with the increasing of the wind velocity. A spectrum analysis basedon MATLAB software is done to the time history curve of the transmission line gallopingobtained by the finite element analysis, and the numerical results agree with the analyticalones. The results prove that the frequency of galloping of the transmission line during theprocess of galloping varies with the wind velocity and span.The study has important guidingsignificance and high value for anti-galloping design.The finite element model of the single-phase and three-phase quad-bundle conductor isestablished based on ANSYS software, analyzing the effect of existing interphase spacerlayout on transmission line galloping and effects of the preventing galloping, which werefound that some layouts can not prevent galloping, the others can prevent galloping. These layouts are based on experience, lack of relevance and theroretical analysis,can not get thebest effect of anti-galloping. The vibration mode is obtained based on spectral analysis andthe displacement vector of conductor galloping. Optimization scheme is proposed accordingto the vibration mode and the effect of anti-galloping under different wind speed is calculated.The effect of anti-galloping of optimization scheme is better than the original layouts. Thestudy provide a basis for anti-galloping of transmission line.