Research On Rainfall Model And Rain Load Effect Of Transmission Line

In terms of the research work of transmission tower-line system, the emphasis is still focused on the aspects of earthquake and wind resistance. And the study of the ability against wind and rain for transmission tower-line system is still in the initial stage; especially the cognition of the adjection of rain load is not enough. It is the current research status which leads to the common damage of transmission tower-line system. The damage results in the blackout and short of water in a small area or even the whole city which cause terrible inconvenience and great economic losses at the same time. There is an urgent need to carry out systematic research on the function properties of rain load and study its influence on transmission line to lay the foundation for the study of transmission tower-line system under the combined action of wind and rain.In the practical engineering application, the impact of rainfall can be decomposed into forces in two directions, namely the vertical direction and horizontal direction(along wind). Thus, the study of this paper is focused on the vertical rain load first. The distribution of rain, the number of raindrops per unit volume and the occupancy of rain in the air are studied on the basis of given rainfall classification. Then, the vertical final velocity models of raindrops used in the literatures are analyzed. And the influences of these factors on vertical rain load are also studied in this paper.The horizontal rain load is induced by the translation of raindrops caused by the effect of horizontal wind. Therefore, two main contents are studied in this part of the article. One is the horizontal final velocity of raindrops; the other is the horizontal rain load. The horizontal final velocity of raindrops with different diameters under several specific wind speeds are obtained by the numerical simulation of horizontal final velocity using Runge-Kutta method. The influences of different wind speeds and different horizontal final velocities of raindrops on horizontal rain load are studied.The horizontal rain load is closely related to horizontal wind velocity. The above study is about the effects of mean wind velocity on horizontal rain load. The total wind velocity consists of mean wind velocity and fluctuating wind velocity. And the fluctuant wind velocity will induce fluctuant horizontal final velocities which causes dynamic rain load. Thus the horizontal movement differential equation of raindrops at different times is established and solved combined with the time history of total wind velocity. And the horizontal final velocity of raindrops and the time-history curves of horizontal rain load are also obtained in this paper.The effects of static and dynamic rain load on transmission line are studied respectively in the last part of this paper. A four-node cable element model is established. The static and dynamic rain loads are applied to the finite element model separately. For the static calculation, the condition with and without wind are discussed under which the influences of different spans and different diameters on the displacement of transmission line are studied. The dynamic responses of transmission line are analyzed in the dynamic calculation part using the Newmark-? method.