Resarch On Influence Of Viaduct On Lightning Strike Characteristics Of Catenary System And Its Near-ground

Lightning accidents often occur on high-speed railway in China,which results in different degrees of economic and personnel losses.Viaducts are widely used in high-speed railway construction in China.After the erection of viaduct,the development path and distribution of lightning development channel will change,which will affect the lightning strike characteristics of catenary system and its nearby ground.The lightning strike characteristics of catenary system and its nearby ground play an important guiding role in lightning protection design.However,there are some deficiencies in the existing research.Therefore,it is of great significance to study the influence of viaduct on lightning strike characteristics of catenary system and its nearby ground.This paper focuses on the following aspects:Based on fractal theory,the lightning fractal path simulation of high speed railway catenary system is realized,and the rationality of the development probability index is verified from the perspective of box dimension method,the rationality of the established model is verified from the point effect and shielding effect of lightning leader in the development process.In addition,the model is simplified based on the characteristics of the upward leader inception of the catenary system,it is considered that the upward leader will not incept in the catenary system before the lightning final jump.The lightning strike rate distribution of catenary system without considering buildings around viaduct is studied.The relationship between lightning strike rate of catenary system and the height of viaduct and the inception position of lightning leader is given respectively.Then,the lightning strike rate distribution considering buildings around viaduct is studied,and the influence rules of the height of buildings and the distance between buildings and viaduct on lightning strike rate of catenary system are clarified.The distribution of ground flash on flat ground and the influence of viaduct on the distribution of ground flash are studied comparatively.Results shown that the distribution of ground flash obeys normal distribution on flat ground,after the construction of viaduct,the distribution of ground flash was divided into complete ground flash shielding area,partial ground flash shielding area,dangerous ground flash area and normal ground flash area.A method for estimating distribution of ground flash near viaduct is proposed,and the influence rule of some impact factors,such as height of viaduct and lightning current amplitude on distribution of ground flash near viaduct was given in this paper.Finally,it is concluded that the shielding range of viaduct to ground increases linearly with the height of viaduct approximately.A three-dimensional electric field simulation model of catenary system of viaduct is established.The influence of steel bars inside the viaduct on the lightning strike characteristics of catenary system is studied.The result shown that the steel mesh structure of viaduct has a certain weakening effect on electric field intensity of the catenary conductor,which leads to the decrease of the lightning strike probability of catenary system.A capacitance equivalent model of viaduct catenary system is proposed,on this basis,the mechanism of lightning-attraction capacity reduction of catenary system caused by the reduction of induced voltage by steel bar structure is explained.