Lightning rods, also known as lightning protection needles, are devices used to protect buildings, tall trees, etc. from lightning strikes. A lightning receptor is installed on the top of the object to be protected, and the wire is connected to the ground leakage network buried in the ground. The lightning rod specification must meet the GB standard. The lightning rod height specification required by each lightning protection category is different.
When the thundercloud discharges close to the ground it distorts the ground electric field. At the top of the lightning rod, a local electric field concentration space is formed to influence the development direction of the lightning pilot discharge, guide the lightning discharge to the lightning arrester, and then the lightning current is led to the earth through the ground down conductor and the grounding device, thereby protecting the protected object from the lightning strike. .
allusion:
The Tang Dynasty's "The Hustle Boss" book records such a thing: During the Han Dynasty, the Boliang Temple was stricken by fire. A wizard suggested that putting a piece of fishtail-shaped copper tile on top of the layer would prevent lightning. The sky fire caused. The roof tiles on the roof that are arranged on the roof are actually used for lightning protection and can be considered as the prototype of modern lightning rods. As far back as before, China already had lightning rods, usually decorated with faucets, and there were lightning rods in the dragon's beak.
China New Things
The book “Chinese New Affairs” written by the French traveler Cabri Odio de Makarin in 1688 records that on both sides of the Chinese roof, there is an upturned faucet. Longkou spits out twisting metal tongues and reaches into the sky. The root of the tongue connects a fine wire to the ground. This wonderful device will show great power at the moment of thunder and lightning. If thunder and lightning strike the house, the current will go from the dragon tongue to the ground and avoid the lightning damage to the building. This shows that lightning protection devices in ancient Chinese buildings are basically similar to modern lightning rods in terms of volume and structure.
Introduction:
The lightning rod is the former name. In the National Standard of the People's Republic of China GB50057-2010 "Lightning Protection Design Code for Buildings," this name has been abandoned and replaced by the "receiving rod". The lightning rod and the flash, the flash, the flash, the metal roof used for the flash, the metal components, etc., are collectively referred to as the air-termination device; the air-termination device and the deflector and the grounding device together constitute the building or External lightning protection devices for structures to prevent or reduce the physical damage and personal injury caused by lightning hitting buildings or structures nearby.
The reason why the lightning rod was renamed the lightning rod was because the previous name was unscientific and did not reflect the principle of the lightning rod. When the lightning rod was first appeared in China, people thought that it could prevent the house from being struck by lightning, so it was called a lightning rod. In fact, the lightning rod protects the building in such a way that it does not prevent the house from being struck by lightning. Instead, it lifts the upper body and then uses its lead wires and grounding devices to introduce lightning currents into the ground so as to protect the building. For this reason, it has also been proposed to rename the lightning rod as a lightning rod, but in general, the name of the lightning rod is the most appropriate.
installation:
If a building is equipped with a lightning receptor but it is not grounded or if the grounding effect is not good, it will cause more damage to the building or its personnel when the lightning is received, and it will be even worse than a building without a lightning receptor installed. Safety. The lightning accident occurred in Kaixian County, Chongqing in 2007 because the roof of the classroom was made of reinforced concrete slabs. The steel bars were not well grounded. When lightning strikes, lightning flash occurred and there was no place to vent, so that the roof and walls of the classroom were opposite. The discharge of personnel caused a tragic accident in which seven students in the classroom died and dozens of people were injured.
According to the requirements of section 5 'Lightning protection device' in GB50057 “Lightning Protection Design Code for Buildings”, the air-termination device can use copper, tin-plated copper, aluminum, aluminum alloy, hot-dip galvanized steel, stainless steel, copper plating on the outer surface. Made of various materials such as steel, as long as it meets the requirements of its minimum section and thickness. In other words, as long as it is not so easy to rust, not easily damaged by wind and rain, most of the common metal materials can be used to make a lightning receptor. Taking the most common iron connection rod as an example, GB50057 requires that its minimum diameter should not be less than 8 mm.
In this sense, the vast majority of construction steel bars on the market, as long as their diameter is greater than 8 mm, can be used to make lightning rods. After installing them, one or two layers of anti-rust paint can be applied to the surface of the steel rods. The price is very low. In this sense, lightning rods are not branded because lightning rods are only a small class of lightning receptors, and any metal component can be used as a lightning receptor. Emphasizing only the role of lightning rods, emphasizing the lightning rods of famous brands, and ignoring the common lightning-receiving effect of other lightning receptors, ignoring the objective fact that the air-termination device could not function without the deflector and grounding device. Harmful, need to be corrected.
It should be noted that there are all kinds of so-called famous brands of lightning rods on the market. Most of them use 'pre-discharge' or 'early discharge' as their selling points. Most of them are imported from abroad and are called 'special lightning rods'. The scope of protection far exceeds the scope of protection calculated in accordance with the principle of the rolling ball method. Its price is very expensive, and it غير مجاز مي باشدts a few tens of thousands of yuan. The so-called scientific principles of these lightning rods have not been recognized so far in mainland China, and their lightning protection effects have not been recognized in practice. Even if such a lightning rod is installed on the building, it is necessary to perform calculations based on the principle of the traditional ball rolling method when lightning protection is accepted. Customers who have purchased such a lightning rod at a high price must be wary of this risk.
Therefore, instead of paying such high prices for such so-called special lightning rods to protect buildings, it is better to follow the scientific principles of the rolling ball method to carefully inspect the site, carefully design, calculate and verify, and honestly implement on-site construction in accordance with national regulations. Ordinary lightning rods, lightning protection and other lightning receptors are used to protect the place, so that it is safe, reliable and economical.
The so-called ball rolling method assumes that a sphere with a certain radius (100 meters, 60 meters, 45 meters, and 30 meters depending on the degree of protection of the building) will roll along the outer surface of the building when the sphere touches only the lightning. When the device and the ground do not touch the parts that need to be protected, the parts are protected by a lightning receptor. In layman's terms, the place where the sphere can be touched is where the thunder can reach, and where the sphere is out of reach is within the protection range of the lightning receptor.
For the calculation of the protection range of the air-termination device, the calculation of a single-connection lightning rod (lightning rod) and two branches is listed in Appendix D of the “Design Principles for Lightning Protection of Buildings” in GB50057 “Range of protection of air-termination by ball method”. Contour rods, two unequal rods, quadruple-height rods arranged in a rectangular arrangement, single-connected flash-connections (flashbands, lightning protection strips), and two equal-height flashovers The scope of the method of calculation of the scope of protection, and draw a related diagram.
For the vast number of technical personnel in the lightning protection industry, according to the method given in GB50057, some simple cases can be calculated manually, but in daily work, it is often far more complicated than the cases listed in the specifications. The on-site situation, such as: the combination of multiple unequal heights and non-regularly arranged lightning rods, unequal lighted lightning conductors, lightning rods, and lightning conductors, and the calculation of these complex conditions The manual method is simply not possible, and GB50057 does not give any specific calculation method. This problem is a technical problem frequently encountered in the lightning protection industry.
invention:
The Franklin modern lightning rod was invented by American scientist Franklin. Franklin thinks lightning is a discharge phenomenon. In order to prove this, on the thunderstorm of July 1752, he risked being struck by lightning, and he flew a kite with long metal wires into the thunderclouds, pulling a silver key at the end of the wire. When lightning strikes, Franklin's hand approaches the key, and a string of sparks is drawn from the key. There is numbness in her hand. Fortunately, the lightning flash down this time was weak and Franklin was not injured.
Note: This test is very dangerous. Do not try it yourself. In 1753, the famous electrician Lichman was unfortunately killed by lightning in order to prove Franklin's experiment. This was the first victim of lightning experiments.
After successfully carrying out the lightning experiments on flying kites, Franklin was studying the consistency between the lightning and the electricity generated by artificial friction. He made an assumption from the analogy of both: Since the artificially generated electricity is absorbed by the cutting edge, So lightning can also be absorbed by the tip. He thus designed the kite experiment, and the success of the kite experiment in turn confirmed his conjecture. He thus conceived that if a sophisticated device can be placed on a high object, it is possible to introduce lightning into the ground. Franklin used this type of lightning protection device: a few meters long thin iron rods were fixed at the top of tall buildings, separated by insulators between iron rods and buildings. Then use a wire to connect to the bottom end of the iron bar. Then lead the wire into the ground. Franklin called this lightning protection device a lightning rod. After trial, it really can play the role of lightning. The invention of the lightning rod was the first technological achievement with significant application value in the early electrical research.
When North America spread and the lightning rod was first invented and popularized, the church used it as an ominous object. It said that it was loaded with such things as Franklin. Not only could it not avoid lightning, it would cause God's wrath and be struck by lightning. However, In Philadelphia and other places, some of the tall cathedrals that refuse to place lightning rods have been struck by lightning in heavy thunderstorms. And the taller buildings than the church were safe in the thunderstorms because they had been fitted with lightning rods.
Since the lightning rod had already begun to show its glory in places such as Philadelphia, it immediately spread to all parts of North America, and later it was introduced to Europe and later it entered Asia.
After the introduction of French lightning rods into France, the president of the Royal French Academy of Sciences, Noray and others began to oppose the use of lightning rods, and later thought that the round head lightning rod was better than Franklin's pointed lightning rod. However, the French still use Franklin's pointed lightning rods. It is said that the French at that time saw Franklin as an incarnation of Socrates. Franklin became an idol for people to worship. His portrait was captured under the pillow, and the peaked cap modeled after a lightning rod became the most modern hat of Paris in 1778.
After the introduction of British lightning rods into the United Kingdom, the British also widely used Franklin's pointed lightning rods. However, after the outbreak of the American Revolutionary War, Franklin's pointed lightning rods seemed to be the symbol of the United States to be born in the eyes of the British. It is said that the then King George II of England was out of wrath against the American revolution and ordered to replace the tip of the lightning rod on all buildings in England with round heads to show that it was incompatible with the pointed lightning rod as a symbol of the United States. It is an interesting thing in the history of lightning rod application.
species:
Direct lightning lightning rod / special lightning rod / advance pre-discharge lightning rod
Direct lightning is applicable to petrochemical warehouses, radio and television stations, gas stations, building buildings, beacons, communications base stations, meteorological stations, military bases, radar machine rooms, and bank buildings. It is particularly suitable for microwave communication stations, radar base stations, and beacons in higher buildings. Taiwan, communications base stations, military bases, radar room, bank building, astronomical meteorological stations and other important places.
Pre-discharging When the lightning rod intercepts the lightning strike, the receiving flash body catches the lightning. Through the lightning waveform processing device, there is a 3mm gap between the shell and the center ground rod to form the coupling capacitance, and the shell is grounded through an inductance coil (center ground rod). When the down-lead is close to the air-termination device, because the frequency is extremely high, the inductor is in an open state, and the capacitor exhibits a short-circuit characteristic to the high-frequency. Therefore, under the action of the coupling capacitor, the electric field intensity on the surface of the lightning receptor rapidly increases until the avalanche process is triggered, thereby enabling In an instant, the lightning current is discharged into the ground so as to effectively achieve the purpose of lightning protection and safety.
Lightning rod / lightning rod / lightning rod / lightning receptor
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