Henan Zonghai Plastic Industry Co., Ltd. , https://www.hnzonghai.com
Three Misunderstandings of Lightning Protection
When it comes to lightning protection, many people may first think of lightning rods, and the concept of "lightning rods" can easily cause everyone to misunderstand the concept of lightning protection.
Misunderstanding 1 lightning rod is used to "lighten"
In fact, the scientific name of the lightning rod is "light-receiving device". It is not used to "avoid lightning strikes" but to "greet lightning." Lightning rods are essentially lightning rods. The protection mechanism is to direct the lightning to itself, and then introduce the current into the ground through the planned path (down-line), so as to avoid the loss of property and life caused by the lightning directly hitting people, trees, buildings and various facilities. accident.
Misunderstanding 2 When it comes to thunder, the farther you should be from the tree, the better
Most people know that they cannot stand under a tree to avoid rain during a thunder. There are certain one-sidedness on the Internet of "far away from isolated big trees" and "the farther away from big trees, the better".
In an open area, an isolated big tree is equivalent to a lightning rod, which has the highest probability of being struck by lightning. If a lightning strikes a big tree and a person is standing under the big tree, it may cause side flashover and step voltage damage, so it is right to "away" from the big tree during a thunderstorm.
Side flashover (closer to the big tree, high voltage can directly penetrate the air and discharge to the human body)
Step voltage (the closer to the point where the lightning current enters, the greater the step voltage)
The protection range of a lightning rod is limited. When a person is too far away from the tree, he is not covered by the "lightning rod" of the tree. In this way, the person may be directly hit by lightning (the human body becomes a "lightning rod").
In reality, lightning accidents often hit people directly, such as lightning strikes in farmland, and people working in farmland are directly killed by lightning. There are two main reasons for this:
1) There is water in the farmland, and its conductivity is better in comparison.
2) In farmland, usually people are high.
In the city, there are many high-rise buildings (generally lightning rods are installed), we do not need to shelter from the rain under the big tree, even if it is generally not dangerous to shelter from the rain under the big tree.
The common types of lightning damage and precautions are as follows:
1. Contact voltage damage, side flashover;
Preventive measures: Do not stand under or lean on isolated big trees; Do not use wired dianhua; Do not touch the conductors / lines that enter indoors from outside.
2. Step voltage damage;
Preventive measures: Do not stand under the isolated tree; stand with your feet as close as possible; do not run in stride.
3. Lightning strikes the human body directly;
Preventive measures: hide indoors, in the car, close the doors and windows; do not stand on high places, such as the top of the mountain, the roof; do not hold objects that increase the height of the human body, such as fishing rods, hoes, umbrellas, etc., reduce the height of the human body (squat) ; Keep away from humid and open areas, such as farmland, river banks, and do not enter the water.
4. Re-injury caused by lightning damage.
Preventive measures: Keep away from flammable materials, avoid fire damage caused by lightning strikes, and avoid falling injuries caused by lightning strikes on trees / building walls.
Misunderstanding 3 Install the "lightning rod", and the lightning protection is done.
Lightning rods are external lightning protection devices and can only protect against direct lightning strikes. When the lightning rod is fired, the lightning current is instantly discharged to the ground through the down-conductor, which will generate a powerful lightning electromagnetic pulse, commonly known as induction lightning. Inductive lightning can cause extensive damage to electrical and electronic systems. With the development of electronic technology, the equipment integration is getting higher and higher, the volume is smaller and smaller, and it is more and more sensitive to induction mines.
Therefore, lightning protection is a comprehensive system, not only to prevent direct lightning, but also to prevent induction lightning. Direct strike lightning has strong destructive power, but it is "point" destruction, while induction mine is "surface" destruction. Lightning rods are essentially lightning rods. After installing a lightning rod, the probability of being struck by a direct strike will be higher. Therefore, for industrial control systems and sensitive equipment, the more the lightning rod is installed, the more inductive lightning protection is required. (Extracted from China National Defense Mine)