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The so-called lightning strike refers to the rapid discharge between a part of a charged cloud layer and another part of a cloud with heterogeneous charges, or a charged cloud layer and the earth.
Second, several forms of lightning strikes:
(1) Direct lightning
(2) Lightning electromagnetic pulses:
1, induced lightning strike
2, lightning wave intrusion
Third, the general law of lightning activities:
Summer is more than in winter, with more in the south than in the north, more in the east than in the west, more hills than plains, more low latitudes than high latitudes, more land than oceans, more land-land transitional belts than cities, and soil resistivity (more Ï) Larger places than soil resistivity (Ï).
Fourth, the main components of the lightning protection device:
(1) Lightning receptors: Lightning rods that directly intercept lightning strikes, lightning protection strips (wires), lightning protection nets, and metal roofing and metal components used for lightning protection.
(2) Downlead: Metal conductor connecting the lightning arrester and the grounding device.
(3) Lightning Arrester: It is a kind of protection device that can release overvoltage energy and limit overvoltage amplitude. When using, install the arrester near the protected device and connect the arrester in parallel. Under normal conditions, the arrester does not conduct (up to only microampere leakage current). When the voltage acting on the lightning arrester reaches the operating voltage of the arrester, the arrester is turned on, and through the large current, the overvoltage energy is released and the overvoltage is limited to a certain level to protect the insulation of the device. After the overvoltage energy is released, the arrester returns to its original state.
(4) Grounding line: The grounding line is a method of electrical protection. It is connected to the earth's stratum for discharge protection. Its role is to quickly introduce current into the earth through the grounding wire when connected equipment is leaking or inductive. The device housing is no longer charged.
(5) Grounding device (grounding body): A conductor buried in soil or in a mixed-phosphorus foundation as a diffuser.
Fifth, the most practical lightning protection method introduced:
A: direct lightning protection
B; lightning electromagnetic pulse protection
VI. Lightning prevention knowledge in daily life and work Introduction:
(1) Lightning days reduce outdoor activities;
(2) Try not to make fixed telephone calls when thundering;
(3) Do not go near outdoor metal objects;
(4) Do not evade under large trees when thundering;
(5) Do not stay at the water-land junction or the transition between hillside and flat;
(6) Do not shower with solar water heaters without any grounding treatment;
(7) Do not go near metal doors and windows, especially if the household is more than 15 meters high;
(8) Turn off the power of household appliances (except for SPD protection and good grounding systems);
(9) Purchasing real estate, such as housing and other types of fixed assets, should be checked whether there is a lightning protection acceptance certificate;
(10) Purchase of electronic products and household appliances should carefully check the installation instructions, and carefully check whether the installation personnel follow the instructions to install
Thunder Introduction
Lightning is an inevitable natural disaster. Lightning is active at any time on Earth. According to statistics, 1800 thunderstorms were created every second. With 600 lightning flashes, 100 of them fell to the ground, causing buildings. The destruction of power generation, telecommunications and video equipment has caused fire, injured people and livestock, caused economic losses of about 1 billion U.S. dollars per year and killed more than 3,000 people. Among them, nearly 400 people in the United States are struck by lightning every year and their property losses amount to 260 million U.S. dollars. On July 20, 1996, thunderstorms continued in the northeast of India and lightning hit a school building in Bihar, killing 15 pupils and injuring many others. Thunder also burned all five people under the tree. Killed four other peasants working in the fields.
China is also a country with frequent lightning disasters. E.g. About 39 people in Linyi, Shandong, suffer from casualties due to lightning strikes. Another example is that Shanbei Village, Gozhuping Township, Xupu County, Hunan Province is a rare minefield. In the past 10 years, 8 people have been killed by lightning, and 115 people were injured (24 of them were seriously injured), and 5 cattle were also injured. Head, killed more than 50 pigs and killed more than 450 poultry, ducks, and geese. The transformer in the village was also destroyed by lightning five times, houses and trees. The fact that crops and fields were destroyed dozens of times is an alarming figure. Another example is that on July 10, 1996, 12 youths from the Huangkeng Stadium in Suizhou City of Hubei Province were collectively attacked by thunder and lightning. Two people died on the spot, and six seriously wounded people were stunned and unconscious. Rescue the hospital, consciousness barriers to more than 10 hours. Therefore, it is very necessary to understand the laws of lightning and to master correct preventive measures and self-rescue methods.
So let us first understand how lightning is formed. Lightning is the phenomenon of discharge in the atmosphere. It is mostly formed in cumulonimbus clouds. The cumulonimbus will constantly move with the changes of temperature and air flow. When friction is generated during the movement, clouds of charged clouds will form, and some clouds will be formed. There is a positive charge and some clouds have a negative charge. In addition, due to electrostatic induction often makes buildings below the clouds. Trees, etc. with opposite sex charge. As the charge accumulates, the voltage of the thundercloud gradually increases. When the thunderclouds with different charges and the earth's projections approach each other to a certain temperature, the electric field between them exceeds 25-30kV/cm, and intense discharge will occur. At the same time there is a strong flash. As the temperature reaches as high as 2000°C during discharge, the air expands rapidly by heat, and the explosion roar occurs. This is lightning and thunder. The size and amount of thunder and the activity are related to the terrain, weather conditions and latitude of each area. In general, there are more lightning in the mountains than in the plains. There are more coastal areas than in the hinterland of the mainland. The higher the buildings, the greater the chance of being struck by lightning.
Lightning strikes are extremely destructive and their destructive effects are comprehensive, including the destruction of electrical, thermal and mechanical properties. According to the different characteristics of lightning and hazards, lightning can be divided into the following four types:
1. Direct lightning
Direct lightning strikes are formed by the discharge between the clouds and the ground projections. Thunder can hit people and livestock in an instant. Large lightning currents flow into the ground, creating a very high voltage to the ground at the point of strike and its connected metal parts, which may directly result in electric shocks with contact voltage or step voltage. In addition, the huge lightning current that strikes thunder directly passes through the lightning strike and converts into a large amount of heat in a very short period of time, causing the burning of flammable materials or causing the metal to melt and splatter and cause a fire.
2. Spherical Ray
A spherical mine is a sphere. Red or very bright white fireball, movement speed is about 2m/s. Spherical lightning can be from the door. window. Chimneys and other channels intruding into the room are extremely dangerous.
3. Lightning induction, also known as induction thunder
Lightning induction is divided into electrostatic induction and electromagnetic induction. Electrostatic induction is caused by the proximity of the thundercloud to the ground and the induction of a large number of opposite charges on the top of the ground projections. After the thundercloud and other parts are discharged, the charge on the top of the protrusion loses its binding, and in the form of lightning waves, it spreads rapidly along the protrusion. Electromagnetic induction is caused by a powerful magnetic field that rapidly changes in the surrounding space after a lightning strike. This magnetic field can induce a very high voltage on nearby metal conductors, causing secondary discharges to the human body and thus damaging the electrical equipment.
4. Lightning intruding wave
Lightning shock waves are lightning waves that are rapidly transmitted along a line or pipe due to lightning strikes on an overhead line or in an aerial metal pipeline. Its propagation speed is 3x108m/s. Lightning invading waves can destroy the insulation of electrical equipment, causing high pressure to drop people's pressure and cause serious electrical shocks. There are many lightning accidents caused by thunder and lightning invading waves, and these accidents account for about 70% of total lightning accidents in low-voltage systems.
Since the threat of thunder and lightning is so great, what methods do we have to prevent the harm of lightning and use it? The main measure to prevent direct lightning is to install lightning rods, lightning protection nets, and lightning protection strips on buildings. Install a lightning conductor above the high voltage transmission line. A complete lightning protection device includes a lightning receptor. Lead wire and grounding device. The above needles, wires, nets, and belts are actually just air-termination devices. The feeder is used to take advantage of its prominent position above the object to be protected, to direct the lightning to itself, and then to discharge the lightning current into the earth through the down conductor and the grounding device to protect the protected object from lightning strikes. When the corrosion of the cross-section of the lightning receptor is more than 30%, it should be replaced. If the lead-in line is broken or the contact resistance of the grounding device is too large, the arrester will not only fail to protect against lightning, but will also attract lightning and increase the chance of the building being struck by lightning. Therefore, the deflector should meet the requirements of mechanical strength, corrosion resistance and thermal stability. Should take the shortest route. To avoid bending, do not use aluminum wire as a lightning deflector. To educate children not to pull off the line to play. In order to prevent the intrusion of lightning into the room along the low-voltage line, the low-voltage line is preferably powered by an underground cable and the metal sheath of the cable is grounded. When using overhead line power supply, install a group of low-voltage valve arresters or protective gaps of 2 to 3mm in the outdoor and ground together with the iron feet of the insulator. The grounding device can be used with the grounding device of the electrical equipment. The grounding resistance must not be greater than 5-30Ω. The valve arrester is mounted on the attracting end of the object to be protected. The upper end is connected to the line and the lower end is grounded. Normally, the gap of the arrester is kept in isolation, which does not affect the operation of the system. When a high-voltage shock wave hits the circuit due to a lightning strike, the arrester breaks down and grounds, thereby forcibly cutting off the shock wave. At this time, the voltage of the object to be protected is Only residual current generated by the lightning current through the arrester and its leads and grounding devices. After the lightning current passes through the gap of the arrester, it recovers the insulation state so that the system can operate normally. In addition, experts from all over the world are currently studying new technologies for eliminating lightning strikes to improve lightning protection efficiency. After years of hard work, some new devices were invented. For example, ionization and lightning protection devices, radioisotope cable lightning rods, high pulse lightning rods, laser lightning protection devices, semiconductor long needle lightning arrester, etc., how these new lightning protection device performance, but also by practice to verify.
In fact, although the threat of thunder and lightning is great, it is not impossible to prevent it. Moreover, if it is properly reformed and utilized, thunder and lightning can also be a blessing. Let us rationally prevent lightning and prevent it from harming us, and we must make reasonable use of it. It benefits humanity
Seven, mine safety knowledge
1. How do you use the appliance at home when thundering?
Cut off the power, unplug the phone, and do not touch the gas pipeline, water pipes and all kinds of electrified devices, not to use the shower head during the thunder and lightning, because the huge lightning will hit the shower along the water. Do not use radios and televisions with external antennas. Do not answer or call. When strong thunder and lightning, do not use the phone.
2. What should I do if we thunder and lightning when we are outdoors?
Do not stay on the high-rise platform, do not enter isolated huts, booths, and do not evade thunderstorms under big trees. If it is absolutely necessary, you must keep 3 meters away from the trunk, squat down and bring your legs together. If there are ants crawling at the head, neck, and hands when the lightning strikes, the hair is erected, indicating that a lightning strike will occur. You should squat on the ground and try to lower your head, because the head is most vulnerable to lightning strikes than other parts of the body. This will reduce the risk of being struck by lightning and remove metal jewelry, hairpins, and necklaces worn by the body. It is not advisable to stay on the water and the water. It is not advisable to wash clothes, fish, swim, and play on the river. It is not advisable to open a motorcycle quickly, ride a bike fast and run wild in the rain.
3. What should I do if I cannot find suitable lightning protection sites in the wild?
Find a low-lying area, squat down with your feet together, put your hands on your lap, and bend forward. Stay away from sharp, isolated objects such as trees, utility poles, and chimneys. It is not advisable to enter isolated huts, guard posts and other low-rise buildings.
4, in the open space hand is not what to take, what sports should not be done?
Should not use an umbrella, it is not appropriate to put metal tools, badminton rackets, golf clubs and other items on their shoulders. Do not swim or engage in other water sports. It is not advisable to carry out outdoor sports such as ball games, climbing, and riding. Leaving the surface of the water and other open spaces as soon as possible, look for places where there are lightning protection facilities. It is not advisable to drive a motorbike or ride a bike on the road.
5, how to prevent lightning in the room?
Close the doors and windows as far as possible away from doors, windows, balconies and outside walls. Do not approach or touch any metal pipe indoors, including water pipes, heating pipes, gas pipes, etc. • Do not use household appliances in rooms without lightning protection facilities, including televisions, computers, wired telephones, active radios, refrigerators, washing machines, microwave ovens, etc. It is recommended to remove all power plugs. Do not use solar water heaters for bathing during thunderstorms. When a lightning strike occurs, it is necessary to cut off the power quickly and promptly report an alarm.
6. How does lightning strike a burn?
The thermal effect of lightning currents can cause electrical burns and charring of the human body. If a person with a lightning strike catches fire, he may splash water on the wounded person or use a thick coat or blanket to wrap the wounded person to extinguish the flame. For those with respiratory and cardiac arrest, do cardiopulmonary resuscitation first and then treat burn wounds. Cool the wound with cold water and cover with a dressing. If there is no dressing, use a clean cloth or clothes. Timely transfer to local hospital for treatment and take anti-shock measures.
Eight, lightning strikes and lightning characteristics
Lightning strikes generally have direct lightning strikes and indirect lightning strikes.
Direct lightning strike: In the thunder and lightning activity area, thunder and lightning directly through the body, buildings, equipment and other electrical shock generated by the phenomenon of electrical discharge.
Indirect lightning strikes: Indirect lightning strikes are mainly direct electromagnetic radiation effects of lightning impulses and lightning currents conducted through conductors, such as intrusion of lightning waves, thunderbolt counterattacks, and other forms of intrusion into buildings, resulting in electric shocks that result in damage to buildings, equipment, or personal injury.
Lightning wave intrusion refers to when thunder and lightning strike, thunder and lightning directly hit overhead metal pipelines or cables with shallow ground, and powerful lightning currents invade the interior along these pipes.
A lightning strike is a direct lightning strike. When a powerful lightning current is introduced into the earth, a very high voltage is generated in its down conductor, grounding body, and metal conductors connected to them. There is a huge potential difference between metal objects, devices, lines, and human bodies that are not connected to them. This potential difference can cause flashovers.
Lightning features:
The discharge time is short, generally about 50 to 100 microseconds, and the inrush current is large. The current can be as high as tens of thousands to several tens of thousands of amperes. The surge voltage is high and the current generates an alternating magnetic field. The induced voltage can reach as high as 10,000 volts, releasing large energy. Instantly increase the local air temperature to several thousand degrees or more, and the impact pressure is large, and the air pressure can be as high as several tens of atmospheres.
Places vulnerable to lightning:
Areas where the water surface and land-water junctions and particularly humid tides are low, where the soil resistivity is relatively small, suddenly places where the resistivity is not continuous, the terrain is high and the wilderness area, the high-rise buildings, and the discharge of conductive dust and hot exhaust gas columns Plants, pipelines, etc. There are a large number of factory buildings with metal equipment inside, buildings that stand alone in the wilderness, trees in the natural world, various metal projections on TV antennas and roofs, and protruding parts and objects of building roofs.
Nine, lightning warning and lightning common sense
The lightning warning signal is divided into three levels, which are respectively represented by yellow, orange and red.
Yellow warning icon: Lightning activities may occur within 6 hours, which may cause lightning accidents.
Defense Guideline: The government and relevant departments perform lightning protection work according to their duties. Pay close attention to the weather and try to avoid outdoor activities.
Orange warning icon: The possibility of lightning activity within 2 hours is very high, or it has been affected by thunder and lightning activities and may continue to occur. The possibility of a thunderstorm accident is relatively high.
Defense Guideline: The government and related departments implement mine emergency response measures in accordance with their responsibilities. Staff should stay indoors and close the doors and windows.
Outdoor personnel should hide in buildings or cars that have lightning protection facilities.
Cut off dangerous power and do not shelter under trees, poles, or tower cranes. Do not use an umbrella in an open space. Do not use farm tools, badminton rackets, golf clubs, etc. on your shoulders.
Red warning icon: The possibility of lightning activity within 2 hours is very high, or there has been a strong thunder and lightning activity, and may continue, and the possibility of lightning disaster accidents is very high.
Defense Guideline: The government and relevant departments perform lightning emergency rescue work according to their duties.
Personnel should try to hide in buildings or cars that have lightning protection facilities and close doors and windows.
Do not touch antennas, water pipes, Wire Mesh , metal doors and windows, exterior walls of buildings, and away from live equipment such as electrical wires and other similar metal devices. Try not to use electric devices such as televisions and telephones without lightning protection devices or lightning protection devices. Pay close attention to the release of lightning warning information.
Tenth, lightning and hedging six characters:
Learn to learn about thunder and lightning protection.
Listen, through various channels, timely listening to lightning forecasting and warning information issued by meteorological departments at all levels.
Observe and pay close attention to observing the changes in the weather. If any unusual phenomenon is found, take immediate measures to prevent lightning.
In the event of a lightning strike or disaster relief, it is first necessary to cut off sources of electricity, gas, and water that may cause secondary disasters.
Save, use some knowledge of the rescue that has been learned, organize everyone to save themselves and save each other, especially for those who are severely struck by lightning.
In addition to personal protection, Bao should also use social disaster prevention insurance to reduce the economic losses of individuals and organizations.
XI. Indoor Lightning Protection:
In the event of strong thunderstorms, one should go to indoor lightning protection as soon as possible to avoid rain, close the doors and windows; Second, try not to TV, telephone, computers, water heaters and other appliances, temporarily unplug the electrical power, signal plugs may be an emergency measure; Do not touch gas pipelines, tap water pipes, and various electrical devices. Fourth, avoid escaping thunderstorms in huts and pavilions where there are no effective lightning protection devices.
XII. Field Lightning Protection:
When thunderstorms occur in the wild, first, do not make yourself the highest point. As soon as possible, leave the top of the mountain, slopes, ridges, rivers, and lakes to avoid crowding together. Select the lowest point and take your feet to the ground and discard the metal conductive objects. The second is not to close to poles, towers, trees, chimneys and wall root lightning protection grounding devices, do not touch the metal pipelines, wires, train tracks, to prevent side flashing, contact voltage and step voltage; the third is to hide in the car It is relatively safe to close doors and windows in trains, ships and ships. It is not advisable to open motorcycles and ride bicycles in the wilderness.
XIII. Emergency protection:
After the human body is struck by a lightning strike, the lightning current will stop the human heart from beating and stop breathing, but as long as the rescue can be resumed in time, the majority can be restored. One must promptly call the hospital or 120 first aid; Second, immediately on-site emergency rescue by cardiopulmonary resuscitation and artificial respiration; Third, timely report to the local meteorological bureau and lightning protection agencies, so that the first time the implementation of thunder disaster investigation.
There are three physiological effects of lightning damage on the human body: First, a strong lightning pulse current through the heart, the victim will have vasospasm, cardiac arrest, severe ventricular fibrillation occurs, so that the cardiac blood supply dysfunction or cardiac arrest Beat; Second, when the lightning current damages the nerve center of the brain, so that the victim stops breathing; Third, when a strong current through the body will cause electrical burns or muscle lightning palsy, in serious cases lead to death.
"suspended animation". Injured people who are usually struck by lightning often experience a sudden stop of the heart and a sudden stop of breathing. This may be a phenomenon of “fly dead†due to a lightning strike. Immediate rescue operations must be organized on the spot, and the injured person should be placed on the ground to carry out an oral operation. Artificial respiration of the mouth, while doing out-of-heart massage.
XIV. Lightning protection engineering measures and regulatory requirements
In order to strengthen and regulate the work of lightning disaster prevention, the State and the province have successively promulgated the "Meteorological Law of the People's Republic of China", "Decision of the State Council on the Establishment of Administrative Approval for Definitively Necessary Administrative Approval Items," and "Measures for the Prevention and Mitigation of Lightning and Disaster Mitigation." The Measures for the Administration of Professional Qualifications for Lightning Protection Engineering, the Regulations for Design Review and Completion of Lightning Protection Devices, and a series of laws and regulations for strengthening the safety of lightning protection have set forth clear requirements for scientific lightning protection. The lightning warning period is short and difficult, and the momentary impact is severe and the disaster is very serious. Therefore, prevention and reduction of flood disasters must adhere to the principle of “prevention first, prevention and control combined,†and adopt engineering technical measures in advance to establish scientific and effective defenses in order to minimize and reduce lightning disasters.
The engineering measures for scientific lightning protection mainly include: 1. Design and installation of lightning protection devices according to national standards and specifications; 2. The installed lightning protection devices should be regularly tested and maintained; 3. The construction of important facilities should be preceded by a lightning risk assessment.
The lightning protection device is an integrated system whose basic components include external lightning protection measures and internal lightning protection measures. External lightning protection measures mainly include lightning receiving devices, deflectors, shields, grounding devices, etc. Internal lightning protection measures include reasonable wiring, equipotential bonding, shielding (isolation), and installation of surge protectors (SPD). The external lightning protection engineering and technical measures mainly serve to prevent direct lightning strikes; internal mine protection engineering and technical measures mainly serve as anti-lightning and lightning induction; and comprehensive lightning protection measures can ensure lightning protection safety.
Scientific and effective lightning protection engineering measures should not only consider the geographical, geological, soil, climatic conditions, and surrounding environment of the lightning protection object, but also must fully consider the situation of the lightning protection object itself (including building height, area, purpose, etc.). Therefore, investigation of geography, geology, soil, meteorology, environment and other conditions and the characteristics of lightning activity and the characteristics of protected objects are the basis for lightning protection. Buildings should be based on their importance, the nature of their use, and the possibility of a lightning accident. The consequences are classified according to the lightning protection requirements.
The lightning protection device of the new project and the main project are designed, constructed and put into use at the same time, which can greatly reduce the input cost and ensure the lightning protection from the source. The new project lightning protection device is designed and constructed by the professional unit of lightning protection engineering, which can ensure that the lightning protection device design and construction comply with national standards and technical specifications.
The lightning protection device of the new construction project shall be designed to detect and eliminate the lightning safety hazard in the process of design and construction through the technical evaluation of the lightning protection professional agency design, construction tracking inspection, and the design audit and acceptance of the meteorological authority. Otherwise, the input cost of the rectification will be high afterwards. It is difficult to construct and even leave unrecoverable permanent safety hazards.
Lightning protection devices that have already been put into use need regular maintenance, and can be used to ensure long-term validity through regular inspections by lightning protection agencies. Generally, lightning protection devices are tested once a year, and lightning protection devices in explosion hazardous locations are tested every six months. Otherwise, the lightning protection device that has failed will not only fail to prevent lightning, but may even become a lightning hazard.
Large-scale construction projects, key projects, and explosion hazardous environments are key targets for lightning protection. Once a lightning strike is applied, the resulting losses and impacts may be enormous. Therefore, when these projects are pre-argued, it is necessary to commission a lightning protection agency to carry out a lightning risk assessment so as to propose targeted preventive measures in advance, improve the efficiency and feasibility of specific designs in the later period, and effectively increase the lightning defense capabilities. Limits to avoid lightning accidents.
Although thunder and lightning are ruthless, humans have the skill to prevent it. We need to improve mine awareness, universalize mine prevention knowledge, standardize installation and use of lightning protection devices, and take scientific emergency measures to avoid fundamental damage to humanity.
Lightning protection knowledge
First, what is a lightning strike (lightning)?