Lightning protection. General provisions. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Electrician

Lightning protection. General provisions. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Lightning protection

As you know, there is no thunder without lightning, and lightning is the most common independent spark electric discharge that occurs when the voltage between the electrodes in a gaseous medium increases, and has a very high power. Therefore, a conversation about electricity in general without mentioning a thunderstorm will be incomplete.

Single thunderclouds can carry charges of different signs, therefore, when oppositely charged clouds approach, an electric discharge occurs between them - lightning. Some clouds can carry both positive and negative charges. Positive charges are usually concentrated in the lower part of the cloud, where larger drops of moisture are concentrated.

Such clouds, as a result of electrostatic induction, induce potentials on the surface of the earth and on ground objects. As a result, the cloud and the surface of the earth form, as it were, two plates of a giant capacitor with a dielectric - air masses between them. As the intensity of the electric field of the charged cloud reaches a critical value, a weakly luminous channel (the movement of electrons) begins to grow towards the earth, called the leader. After the leader passes through a part of the airspace, there is a pause, during which the accumulation of electric charges increases, and only after that the leader’s advance to the ground resumes, then again a pause, etc. As soon as the leader reaches the surface of the earth or objects rising above the ground, an electric discharge occurs .

Moreover, the discharge does not depend on a person and is not controlled by a person, this is not an artificial lightning discharge created in the laboratory to study this natural phenomenon, and even there one can expect any surprises from lightning. The voltage between the clouds and the ground can be 100 V, the current strength at the moment of a lightning discharge reaches 000 A, the action time is 000-500 s - these data are determined experimentally.

There is nothing top secret about lightning. However, the knowledge gained in the process of researching this phenomenon did not at all reduce the danger of a lightning discharge for human life, but helped teach a person to protect himself from it. The first device to protect buildings from lightning strikes, the lightning rod, was designed back in the middle of the XNUMXth century by Georg Richmann, a professor at St. Petersburg University. When testing this device, the designer himself died, but the principles he laid down in the design of the lightning rod are not only not forgotten, but also serve people for many years, annually saving more than one thousand people from death. Everything ingenious is simple: the scientist grounded lightning, showing it the shortest and easiest way to the ground - along a metal rod.

The vast majority of lightning (about 95%) have a negative polarity. During a thunderstorm, a strong electric field arises near the earth's surface, the intensity of which is especially high at the ends of pointed objects. During a thunderstorm, a visible glow appears on such spiers.

Lightning discharges of positive polarity are rare. They are characterized by a very high current strength - up to 200 A. The path length of linear lightning can reach several kilometers.

In addition to linear, ball lightning occurs in nature, which is a fireball with a diameter of 10-30 cm, slowly moving in the air (at a speed of about 2 m / s) in the direction of the wind. The movement of lightning is accompanied by a whistling or hissing sound. Ball lightning can exist from a few seconds to 4 minutes. Ball lightning usually disappears silently, but sometimes an explosion can occur. Ball lightning enters the room through open windows, vents, doors, stove chimneys and even through cracks. When in contact with a person, it causes severe burns, often leading to death. When ball lightning explodes, a large amount of heat is released, which often leads to fires.

Lightning rods, used to protect buildings and structures from direct strokes of linear lightning, are ineffective against ball lightning. To prevent the penetration of ball lightning into the premises during a thunderstorm, windows, doors, chimneys should be well closed, and ventilation openings should be equipped with a metal mesh with cells of 3-4 cm2. Such a grid is made of copper or steel round wire with a diameter of 2-2,5 mm and is reliably grounded. Lightning most often strikes at places where groundwater comes to the surface, at the junction of earth rocks of different electrical conductivity, exhaust gases and smoke from pipes (due to increased air ionization), as well as at the most elevated parts of buildings and structures above the ground.

Lightning also strikes in places with high electrical resistivity, for example, in the ground, where metal pipelines or cables are laid, where there are inclusions of soil that conducts electricity well (for example, clay). Lightning protection against direct lightning strikes is a complex of protective devices designed to ensure the safety of people, the safety of buildings and structures from possible explosions, fires and destruction that occur when exposed to lightning.

A device that perceives a direct lightning strike and diverts the lightning current to the ground is called a lightning rod. A lightning rod is a metal device that rises above the protected object. It consists of a lightning rod, a supporting structure, a down conductor and ground electrodes.

Author: Korshevr N.G.

See other articles Section Lightning protection.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

Hand dryers spread bacteria 05.05.2016

Everyone knows that regular hand washing is essential to protect yourself from a host of bacteria and viruses. And scientists from the University of Westminster (UK) decided to check how important it is to dry them properly after that.

Researchers have found that modern jet hand dryers are actually no better than "old-fashioned" hand dryers or paper napkins. The fact is that these devices, capable of quickly drying hands, at the same time carry bacteria with an air stream at a speed of 690 km / h at a distance of up to three meters. Studies have shown that jet dryers spread about 20 times more viruses than slower older models blowing warm air. And compared to paper towels, jet dryers spread 1300 times more viruses and bacteria!

During the experiment, scientists tested 3 methods of drying hands: paper towels, conventional hand dryers, and faster jet dryers. It turned out that jet dryers can spread viruses with a powerful stream of air at a distance of up to three meters, conventional warm air dryers - only 75 centimeters, and hand wipes - only 25 centimeters. However, experts from Dyson, which produces the Airblade jet dryer, disagreed with the test results.

First of all, they did not like the experimental methodology, according to which the British "soiled" their hands in a solution with viruses, and then dried them using one of three methods. Dyson believes the study was lobbied by paper towel manufacturers and conducted in artificial environments with unnaturally high levels of viral contamination, and people routinely wash their hands with soap and water before using the dryer.

Other interesting news:

▪ OKI LED printer with white toner

▪ Infrared LEDs vs Face ID

▪ Restoration of the appearance of a person by his DNA

▪ The oceans are rapidly cooling

▪ DNA from the air

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Welding equipment. Article selection

▪ article Rest from deeds (works). Popular expression

▪ article How, according to the views of the Pelasgians, did the Universe originate? Detailed answer

▪ Geologist article. Job description

▪ article Microcontrollers. Directory

▪ article Relay protection. Protection of overhead lines in networks with a voltage of 110-500 kV with an effectively grounded neutral. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews