Study On Iced Conductor Galloping And Influence On Dynamic Properties Of Transmission Tower-Line System

Icing conductor galloping is of great danger to the safe operation of the transmission line. Both at home and abroad, a lot of research work about the mechanism and protection of the conductor galloping has been done. Based on the research results of the experts both at home and abroad, the mechanism of galloping and the adverse impact on the transmission tower and conductors are analyzed. The research work in this paper will be helpful to the in-depth understanding of the mechanism of the conductor galloping and the influence on the transmission lines. It is also of great reference values to the "West-to-East Power Transmission, South-and-North Transaction and Nationwide Electricity Interconnection" and the construction and operation of UHV and EHV transmission lines.In this paper, based on the"catenary curve"theory and the"parabolic"theory, the static property of the overhead transmission conductors is firstly analyzed, and then the influence of meteorological conditions (such as wind, temperature and so forth) on the static property is also analyzed. Based on the"catenary curve"theory, the software used for the analysis of the static property of the overhead transmission conductors is developed with VC++6.0. Based on the actual parameters of Hubei Zhongshankou large span, the tensile forces and shape of the conductors in different meteorological conditions are calculated, and the impacts of temperature, ice thickness, and wind speed on the tensile force of conductors are analyzed. The analysing results show that, compared with temperature and wind speed, the ice accretion has the greatest influence on the tensile force and configuration of conductors.According to the characteristics of the uneven ice accumulation and the non-contemporaneous ice shedding, the imbalance tensile forces of conductors in the same dead-end section are analyzed. As to the uneven ice accumulation, when the heavy icing spans are in two ends of the dead-end section, the straight-line towers near the dead-end tower bear the largest imbalanced tension. As to the non-contemporaneous ice shedding, when the light icing span is in the middle of the strain section, the arc altitude of the light icing span is the largest. Therefore, the key positions of new established transmission towers should be reinforced according to the meteorological conditions.Based on the the hydromechanical theory, the modelling method and the simulation method for the analysis of the aerodynamic properties of the typical iced conductor (crescent iced conductor) is put forward. The air flow map around the iced conductor is simulated. Besides, as to the iced conductors with different ice thickness, the lift coefficient, drag coefficient and torsion coefficient under different attack angles are calculated. The influence law of ice thickness and wind speed on the aerodynamic parameters of iced conductors can be obtained, which is consistent with that reported in existing related literatures. Consequently, the fluid calculation method can substitute the wind tunnel test to acquire the the aerodynamic parameter of the iced conductors, which can avoid massive test work and save the manpower and material resource.Considering the disadvantage of conventional one-degree-of-freedom galloping mechanism, the three-degree-of-freedom mechanical model considering the iced conductor's coupling vibration in the direction of vertical, horizon and torsion is put forward. The three-degree-of-freedom control equation is established, and the solving method of combining analysis and Simulink simulation is put forward. The solving method can not only solve the three-degree-of-freedom control equation, but also immediately obtain the time-history curve and galloping track. Take the Hubei Zhongshankou Yao-Shuang transmission line as example, the time-history curve and galloping trace is analyzed. The results show that, under steady galloping state, the time-history curves of the horizontal and vertical directions are approximately simple harmonic waves. The frequency of the transverse vibration is consistent with that of the torsional vibration. It can be seen from the galloping track that, the main vibration is in the vertical direction, the amplitude in the horizontal direction is small, and the galloping track is approximately an oblique ellipse.Based on the existing tensile force calculation method, the calculation formula of the maximum varing quantity of the horizontal tension and the vertical tension component at the suspension poin are deduced. And the influences of the galloping parameter and the line parameter on the tension varing quantity are analyzed. The calculation formula can be used to estimate the maximum varing quantity of the tension in the two directions, which can provide foundation for the design of the supporting structures (such as transimission tower). Based on the balance equation of the vibration, taking the vibration displacement as the constraint and taking the vibration frequency as the random variable, the safe boundary equation of the vibration problem of the transmission tower is deduced, and then the reliability design method is proposed.