Chinese name
lightning rod
mbth
lightning rod
lightning protection needle
inventor
American scientist Franklin
uses
devices to protect buildings and other lightning strikes
types
direct lightning strike type, special type and pre-discharge type < The tile decoration at the beginning of fishtail on the roof is actually used as lightning protection, which can be considered as the embryonic form of modern lightning rod. As early as in the past, China already had a lightning rod, usually decorated with a faucet, with a lightning rod head in the dragon's mouth.
New Things in China
In the book "New Things in China" written by French traveler Cabriobe Demaganlan in 1688, it is recorded that at both ends of the roof of China, there is an upturned faucet, and the dragon mouth spits out a tortuous metal tongue, which extends to the sky, and the root of the tongue is connected with a thin wire, which goes straight to the ground. This wonderful device shows its magic power at the moment of lightning. If lightning strikes a house, the current will travel from the dragon's tongue to the ground to prevent lightning from destroying the building. This shows that the lightning protection devices in ancient buildings in China are basically similar to modern lightning rods in mass and structure.
Introduction
A lightning rod
The lightning rod was called in the past, but it has been abandoned in the Chinese people's national standard GB557-21 "Code for Lightning Protection Design of Buildings" and replaced by "lightning rod". Lightning rod, lightning belt, lightning wire, lightning net, metal roof and metal components used for lightning connection are collectively called lightning receptors; The lightning arrester, down lead and grounding device together form the external lightning protection device of the building or structure, which is used to avoid or reduce the physical damage and personal injury caused by lightning striking on or near the building (structure).
the reason why the lightning rod was renamed as lightning rod was because the previous name was unscientific and did not reflect the principle of lightning rod. When lightning rod first appeared in China, people thought it could prevent houses from being struck by lightning, so they called it lightning rod. But in fact, the way of lightning rod to protect buildings is not to prevent houses from being struck by lightning, but to attract lightning to the upper body, and then introduce lightning current into the ground through its down lead and grounding device, thus playing a role in protecting buildings. It is for this reason that some people suggest that the lightning rod be renamed as the lightning rod, but in general, the name of lightning rod is the most appropriate.
if a building with
lightning arrester is installed, but it is not grounded or the grounding effect is not good, it will cause greater damage to the building or people in it when lightning arrester is installed, which is even more unsafe than a building without lightning arrester. In 27, the lightning accident occurred in Kaixian County, Chongqing, because the roof of the classroom was made of reinforced concrete slabs, and the steel bars in it were not well grounded, so they were caught in lightning and had nowhere to be released, thus discharging indoor personnel through the roof and walls of the classroom, resulting in a tragic accident in which seven primary school students were killed and dozens injured.
according to the requirements of chapter 5' lightning protection device' in the code for lightning protection design of buildings (GB557), the lightning arrester can be made of various materials such as copper, tinned copper, aluminum, aluminum alloy, hot-dip galvanized steel, stainless steel, steel with copper plating on the outer surface, and so on, as long as the requirements of its minimum cross section and thickness are met. In other words, as long as it is not so easy to rust and be easily damaged by wind and rain, most common metal materials can be used to make lightning receptors. Taking the most common iron lightning rod as an example, GB557 requires that its minimum diameter should not be less than 8 mm..
in this sense, the vast majority of building steel bars in the market can be used to make lightning rods as long as their diameter is greater than 8mm, and only one or two layers of antirust paint need to be painted on their surfaces after installation, which is very cheap. In this sense, lightning rod has no brand, because lightning rod is only a small class of lightning receptor, and any metal component can be used as lightning receptor. Only the role of lightning rod is emphasized, and the famous brand lightning rod is emphasized, while the same lightning receiving function of other lightning receivers is ignored, and the objective fact that lightning receivers cannot function without down lead and grounding device is ignored. This concept is harmful and needs to be corrected.
It should be noted that there are various so-called well-known brands of lightning rods in the market, most of which are so-called' special lightning rods' imported from abroad, and their claimed protection range far exceeds the protection range calculated according to the principle of rolling ball method, and their prices are very expensive, with tens of thousands of yuan each. The so-called scientific principles of these lightning rods have not been recognized in Chinese mainland so far, and their lightning protection effect has not been recognized in practice. Even if such a lightning rod is installed on the building, it should be calculated according to the principle of traditional rolling ball method when lightning protection is accepted. Customers who have bought such a lightning rod at a high price should be wary of this risk.
Therefore, instead of paying a high price for such so-called special lightning rods to protect buildings, it is better to carefully investigate the site, carefully design, calculate and verify it according to the scientific principle of the rolling ball method, and honestly carry out the site construction according to the national standards, and use ordinary lightning rods, lightning strips and other lightning receptors to ensure that the protected places are in place, so as to achieve the purpose of being safe, reliable and economical.
the so-called rolling ball method assumes that a sphere with a certain radius (1 meters, 6 meters, 45 meters, 3 meters depending on the protection level of the building) rolls along the outer surface of the building. When the sphere only touches the lightning receptor and the ground, but not the part that needs protection, the part will be protected by the lightning receptor. In layman's terms, the place where this sphere can touch is the place where lightning can hit, and the place where the sphere can't touch is within the protection range of the lightning arrester.
the calculation of the protection range of lightning arrester is listed in appendix d' determining the protection range of lightning arrester by rolling ball method' of GB557 "code for lightning protection design of buildings", which includes calculating a single lightning rod (lightning rod), two equal-height lightning rods, two unequal-height lightning rods, four equal-height lightning rods arranged in a rectangle, a single lightning wire (lightning belt and lightning belt) and two equal-height lightning rods.
according to the method given in GB557, technicians in the lightning protection industry can manually calculate some simple situations, but in their daily work, they often encounter field situations that are far more complicated than the cases listed in the specification, such as: the combined protection range of multiple lightning rods, lightning wires, lightning rods and lightning wires with different heights, and the calculation of these complex situations. This problem is a technical problem often encountered in lightning protection industry.