Some users installed 0.5-2 meters long iron rod on outdoor antenna as lightning rod, which did not play the role of lightning protection. Instead, the lightning is led to the TV antenna and uploaded to the TV, resulting in the destruction of the machine and the death of people. The lightning rod is actually a lightning rod. It leads lightning charges in the air to itself. Then the earth is introduced through wiring to protect other objects from lightning. The introduction of lightning voltage into the TV set will make the TV set bear lightning high voltage of hundreds of thousands of volts to millions of volts, which will inevitably destroy the TV set; If someone had been watching TV, the audience would have been killed by lightning. Therefore, the lightning rod installed on the outdoor antenna of TV set must be removed. When using the indoor antenna, you can watch TV programs as usual in rainy days. However, when using outdoor antenna, lightning protection device should be installed and grounded reliably in rainy days, otherwise it is not suitable to watch. At the same time, the outdoor antenna plug must be unplugged from the TV set, and the outdoor antenna should be grounded to prevent the lightning antenna from damaging the TV set and endangering personal safety.
History of lightning rod
Lightning is the most common natural phenomenon on earth. On average, there are more than 100 lightning strikes on the whole earth surface every second. The center temperature of lightning can be as high as 17000 ~ 25000℃, and within110 second, millions to hundreds of millions of joules of energy are released ... A long-distance lightning will fall to the ground after about 50 laps, leaving a winding track in the air. When lightning strikes, the current can jump to 10000 amps, bringing 5 coulombs of electricity to the earth. The shapes of lightning are dendritic, strip, sheet, bead and ball. Among them, the rare spherical lightning attracts the most interest of scientists. 1000 lightning observation records were made in the 9th century. There are various colors, the most common ones are red, orange and yellow. The moving speed is relatively slow, and the existing time is between 1 and 5 seconds. After the fireball disappears, it will explode violently, with great destructive power. August 1989, 15, Huangdao oil depot in Qingdao, China, was attacked by spherical lightning, and the oil storage tank exploded. American scientists have observed 6.5438+0.2 million lightning photos in the North American Grassland Meteorite Observation Network, and think that spherical lightning is separated from the end of ordinary lightning, and spherical lightning is "the condensate of excited metastable molecules and plasma".
The invention of lightning rod has a history of more than 240 years. Because of its protection, thousands of high-rise buildings have got rid of the threat of lightning and made contributions to human civilization and prosperity. Later, King George III ordered Britain to use a lightning rod with a spherical top, and the French made the head of the lightning rod conical. The United States, on the other hand, has always insisted on using Fourier-tip lightning rods. According to The New York Times, the new lightning rod used in the United States today looks like a feather duster, with 2,000 thin wires sticking out from the top. The wires are radial, which can disperse the static charges gathered around the building and have strong lightning protection ability. The semiconductor lightning arrester invented by Professor Xie Guangrun in China is also a new lightning protection device.
Our clever ancestors invented lightning protection devices long before the West and put them into practice. According to the Book of the Later Han Dynasty, an important palace, Weiyang Palace and White Balcony, was struck by lightning and soon caught fire. An alchemist named Yong Zhi suggested to Emperor Wu of Han Dynasty that a "shark" should be installed on the roof of the palace to prevent disaster. In the next two thousand years, this metal tile ornament was mostly installed on the roofs of ancient buildings in China, including dragons, flying fish and cocks. Although there is no wire grounding, the eaves and walls wet by heavy rain naturally play a role in grounding. Because this kind of tile is higher than the building, even fierce lightning strikes generally only destroy the tile and preserve the main body of the building.
Around the Three Kingdoms period, craftsmen have realized the importance of grounding. When they built an ancient pagoda much higher than ordinary buildings, they installed a "gourd string" made of steel at the top, naturally focusing on lightning protection. Moreover, it is connected with the tower core column coated with metal powder, which is easy to conduct electricity. The lower end of the column is provided with a dragon cave for storing metal, which constitutes a very complete lightning protection device. For example, the Baosheng Temple Tower in Gaochun County, Jiangsu Province was built in the Three Kingdoms period in 229 AD, with a height of 3 1.5 meters, much higher than the surrounding buildings. Because the 4-meter-high iron temple is installed at the top of the tower, it consists of a bowl, a wheel and a gourd. After thousands of years of wind and rain, it has never been struck by lightning. In the Ming Dynasty, a complete lightning protection device consisting of metal poles and grounding wires appeared. 1688, a western missionary, Makalian, came to China and wrote in China's Notes: "On the roofs of some buildings in China, there is an ornament called dragon, with its head tilted to the sky and its mouth open. The tongues of these monsters are a sharp metal core, and the other end is connected with the buried metal, which allows lightning to run to the ground without damaging the building. " According to this westerner's record, it was more than 70 years earlier than Franklin!
Structural characteristics of lightning rod
Conventional lightning protection device and its development
1750, Franklin proposed a lightning rod for lightning protection, which releases charges through the tip of the needle and slowly neutralizes the charges in the thunderstorm cloud. Later practice proved that it can't "lightning", but lead lightning to itself to protect the surrounding equipment. Later, after repeating Franklin's famous kite experiment (his friend Lichtman used him to do the experiment and was killed by direct lightning), Russian lomonosov also made an important argument in his paper (a speech on atmospheric phenomena caused by electricity) published in 1753. An important little-known fact is that shortly after Franklin published the theory of lightning rod, a French engineer built a lightning rod according to his theory, and lightning struck soon. This is the first time that human beings have actively tried to change the way of lightning, and it is also proof that direct lightning can be protected. As an upright scientist, the French engineer immediately reported the success of Franklin lightning rod.
The practical application of lightning rod must solve the problem of its protection range. This has been gradually quantified in laboratory and practical application for many years, and its accuracy has basically met the needs of engineering design. It is the development of high voltage transmission and power system in various countries that promotes the progress of this scientific research work.
1925- 1926, Peek used the lightning rod model of "artificial lightning" discharge for the first time in the laboratory. The relationship between protection range-protection coefficient and the ratio of Lei Yun height to needle height (H/h) and the influence of Lei Yun polarity on protection coefficient were studied. 1930- 1934, countries began to widely use lightning rods to protect power plants and substations. At that time, 230KV power grid had appeared for many years, and 287KV EHV power grid was under construction. For example, the American Gas Electric Company (AGE) began to protect substations with lightning rods and wires at 1934. The protection scope of the lightning conductor is determined as follows: when the structural strength is sufficient, the hanging height of the lightning conductor should be increased by 0.3 m every 0.45 m protection horizontal distance; When the structural strength is limited, the protection horizontal distance should be increased by 0.3m every 0.6m. This corresponds to the protection angles of 56 and 64 respectively. This is close to the lightning protection standard of Japan in the late 1960s. In the early 1960s (1963 Davis), in the early 1970s, the United States, Britain and other countries put forward the hit distance theory, which considered the magnitude of lightning current to select the protection range. China's high-voltage workers (under the guidance of Professor Zhu Mumei and Comrade Wang Xiaoyu) also put forward a similar method when studying lightning protection of transmission lines in 1962~ 1964. Regarding the protection of power plants and substations, in the 1950s, China only used lightning rods, for fear that the disconnection of lightning rods would affect the whole power plants and substations. It was not until the mid-1970s that it was clear that lightning wires could be used to protect power plants and substations.
Franklin, inventor of lightning rod
1749 bordeaux academy of sciences offered a reward to find the answer to such a question: "what is the similarity between electricity and thunder?" A doctor named Babaret declared in his paper that electricity and thunder are the same thing. His paper won the prize for it.
In Philadelphia, USA, there was a scientist named Franklin. One day, he did a sensational experiment.
He made a big kite out of silk, and tied a thin iron wire at the top of the kite. The iron wire was connected to the kite-flying thread, and a ribbon was tied at the other end of the thread, and a key was hung between the ribbon and the thread. Franklin flew a kite when it was raining and thundering outside. Suddenly, lightning hit the kite, and the current passed through the wire to the key. At this time, Franklin had an idea: since electricity comes down slowly along the kite line, can you build a ladder for electricity on the tall building and let it come down obediently? In this way, the building will not be damaged by tall buildings.
First, he did an experiment in his own home: he installed a three-meter-long thin iron bar with a pointed tip on the chimney on the roof, tied a metal wire to the lower end of the thin iron bar, and led the metal wire along the stairs to the water pump at the bottom of the building. Divide the wire through the room into two sections, each with a small bell. When lightning enters from a thin iron bar and two wires are stressed, Jason Chung will shake and make a noise.
One day, a storm came. Accompanied by thunder and rain, Franklin, who was waiting by the little bell, heard the crisp and pleasant sound of the little bell. He smiled happily. Franklin called that thin iron bar a lightning rod.
The invention of lightning rod aroused the opposition of the church. They think that pointing the sharp pole on the roof to the sky is disrespectful to God and should be punished by God. However, after a thunderstorm, the church caught fire, but the house with lightning rod was safe, so the lightning rod was quickly accepted by people. Now, lightning rods are installed in high-rise buildings.
In the second year of the kite experiment, Franklin invented the lightning rod. The solution is to erect a metal pole 2 to 3 meters high on the roof and connect it with the ground with metal wires. When lightning meekly flows underground along the metal wire in thunderstorm weather, the building will not be struck by lightning.
In order to promote the use of lightning rods, Franklin wrote an article entitled "How to protect houses from lightning". After the article was published, American cities immediately began to install lightning rods. But this was opposed by the priests, who said that lightning was the wrath of God. Lightning rods also met with strong opposition in France. The residents of St. Omer sued the local people who installed lightning protection devices, and they were afraid to punish this blasphemy.
Lightning rod is the first technical achievement with great application value in early electrical research. It not only protects mankind from the ravages of "Lei Gong", but also isolates lightning from God.