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Lightning protection in summer

Lightning protection in summer
At present, the thunderstorm weather in summer is approaching, and the prevention of lightning strikes is the primary problem for our human beings. Over the past few years, the number of people killed by lightning or indirect lightning strikes has been growing. How to prevent lightning strikes is something that people often talk about. In summer, lightning is divided into two kinds of hazards, one is direct lightning strike, the other is indirect lightning strike. Direct lightning strikes are far more harmful than indirect lightning strikes, which we all know. The indirect lightning stroke is mainly caused by tens of thousands of volts of ultra-high voltage discharge induced by the strong electromagnetic field generated by the charge in the thunderstorm cloud layer when discharging through the metal wire. Next, we will elaborate on lightning protection in more detail.
1. Direct lightning strike
The protection against direct lightning strike has been described in many professional textbooks. The method is to build lightning protection measures, set up metal lightning protection conductors on tall buildings, which can release the huge charge of thunderstorm clouds. Or large lightning protection towers are installed around the residential areas to prevent human life and property from being damaged and lost. In thunderstorm weather, try to stay away from those tall tree forest areas and buildings without lightning protection measures, as well as overhead high and low voltage power transmission networks and communication networks. When the thunderstorm is coming, the best lightning protection method is to hide in the house as soon as possible, and close the doors and windows to prevent spherical lightning from entering. If you encounter thunderstorms in the wild, you should first look at your geographical location. Don’t go to high places, enter low-lying areas as soon as possible, and find a place that can shelter from rain to avoid lightning strikes.
2. Induction lightning
For inductive lightning, the general people do not know much about it. Only professionals know the potential hazards of inductive lightning. What is inductive lightning? It is the charged thunderstorm cloud layer that generates an instantaneous strong high pulse electromagnetic field when discharging. This strong magnetic field will generate induced charges in the metal wires around us. Due to the accumulation of induced charges, a high potential difference to ground will be formed on the metal wire, which is what we usually call high-voltage electricity. Do you know the potential of high-voltage transmission network? Its approximate range is between 10 kV and hundreds of kV potentials. Please don’t underestimate the inductive lightning strike. There is still a lot of knowledge here. I will tell you a short story from real life;
During an accidental strong lightning discharge, we learned about the transient strong magnetoelectric conversion process caused by strong lightning. It was the summer of 1985. One resident’s outdoor TV antenna was about 6m high, and the antenna height was not higher than the height of nearby buildings and trees. According to visual inspection, the height of trees is 10 meters, the height of buildings is 8 meters, while the vertical height of the cumulonimbus cloud layer from the ground TV antenna is more than 100 meters, and the effective distance from the occurrence of strong lightning is 1000 meters. In thunderstorm weather, ordinary bungalow residents will unplug the TV antenna and TV power plug. The distance between the unplugged antenna connector and the TV terminal is about 20cm. The length of the TV antenna feeder is not more than 20m. The antenna receiver is a simple civil dipole antenna. Suddenly, after a flash of light, a huge thunder burst from the sky about 300 meters away, and I heard a “pop” behind the TV! An arc light flashed. When I looked near, the TV antenna connector and the surface of each terminal of the TV had been damaged by high-voltage arc. At that time, all the people in the room were shocked by the sudden discharge sound, and they were glad that they were far away from the TV, otherwise, the consequences would not be imagined. Calculated according to the distance of 20cm, 10000V high-voltage power can break through the dry air medium at a distance of 1cm, while the breakdown voltage of the air medium at a distance of 20cm should be about 200000 V. Because it was a thunderstorm at that time, the air humidity in the room was relatively high, and the voltage to break down the 1cm air medium should be about 7000 volts, so the voltage to break down the 20cm air medium should also be more than 100000 volts. The above data is only a rough calculation, but we still need to do further research on how high the magnetic induction charge can be generated on the double 20 meter long metal conductor.
Although the story is over, our specific measures to prevent thunder and lightning are not complete. Through the above short story, we know the indirect harm of inductive lightning. In the thunderstorm season, we should try our best to stay away from the fixed buried lead wires of high and low voltage transmission networks, overhead communication networks with metal conductors and various communication transmission towers. It also includes the radio receiving antenna and other metal wire networks, which must be far away from and do not touch the metal ends of their pendulous extension lines. In all the overhead metal conductive networks in our urban and rural areas, they stretch around us for tens or hundreds of miles. The amount of lightning induced charge generated above it is very high. In an instant, it can induce voltage up to tens of thousands of volts, which will instantly destroy the electrical and electronic equipment connected with it. Next, we will use a list to explain some problems that should be noticed when thunderstorms come.
1. Keep away from tall buildings and trees and try to enter low-lying areas.
2. Keep away from high and low voltage transmission network.
3. Metal extension fixture (metal tension wire) far away from the power transmission network.
4. Keep away from all metal wire communication networks.
5. Keep away from various metal facilities of communication tower.
6. Keep away from various overhead metal building facilities and metal materials stored indoors and outdoors.
7. Do not touch the metal ends of various conductors extending outdoors and indoors, and try to keep away from them.
9. Try not to get out of the car during driving.
10. When encountering thunderstorm, try to put away the metal objects in your hands, even pay attention to the metal lines for drying clothes, and try to take the clothes to the house when the thunderstorm comes.
11. Before the thunderstorm, disconnect all equipment leads connected to the outdoor. The best disconnection control device is set outdoors. Never touch the metal parts of these breakpoints.
We have basically scribbled about personal protection in thunderstorm season. In any case, it is the most important to protect your life in the thunderstorm season. Adults must repeatedly warn children and tell them about lightning protection in thunderstorm season.