The lightning rod consists of a flash picker, a grounding lead line and a grounding body of 3 parts.
The flashover usually uses a round steel or steel pipe with a diameter of 15~20mm and a length of 1~2m, which is fixed to the upper end of the pillar and connected to the grounding body by grounding the downline. When the Thundercloud discharge channel is developed to the near ground, because the tip of the lightning rod protrudes the ground and has good grounding, the electric field intensity near the tip of the needle increases, accumulates the opposite polarity of the charge, and guides the discharge. In turn, the building or instrument is prevented from accumulating too much charge and is struck by lightning. Generally speaking, lightning will not directly hit the lightning rod, and the lightning rod itself if struck by lightning also has the risk of melting and explosion. Lightning Rod has a certain protective effect. The calculation method of the protection scope is determined by the operation experience and the experimental results of the laboratory model. The common method in engineering design is to think that the protection radius is a function of the height of the lightning rod. According to Chinese regulations, the protection range of a single lightning rod is a cone (see chart).
A lightning rod with a height of h with a protective radius of r=1.5h on the ground; on a horizontal surface with a HX height of the protected object, its protective radius rx is
When Hx≥, rx= (H-HX) P=h0P
When hx<, rx= (1.5H-2HX) P
When h≤30m, P=1
Since the 60 's, the strike distance method for calculating the protection range of lightning rod has been put forward, and it is considered that the protection range is also affected by the size of lightning current.
But so far, there is no perfect way to calculate the scope of protection that is recognized by scientists and engineers all over the world.