There is a rapid discharge between a part of a charged cloud and another part of a cloud with a different charge, or between a charged cloud and the earth. This rapid discharge process produces intense lightning accompanied by a loud sound. This is what we see as lightning and thunder.
Of course, the discharge between clouds is mainly harmful to aircraft, and does not have a significant impact on buildings, people and animals on the ground, whereas the discharge of clouds on the earth is very harmful to buildings, electrical and electronic equipment, and people and animals.
Usually there are three main forms of lightning strikes: one is a charged cloud and a point on the ground between the rapid discharge phenomenon, called "direct lightning". The second is a charged cloud due to electrostatic induction, so that a range of the ground with a heterogeneous charge. When the direct lightning occurred, the cloud charged to disappear quickly, and some ranges of the ground due to the high resistance of the scattering, so that the local high voltage, or due to the direct lightning discharge process, a strong impulse current on the surrounding wires or metal objects produced by electromagnetic induction of high voltage and flash phenomenon is called a "secondary lightning" or "induction lightning". "Induction lightning". The third is "spherical lightning".
The power of lightning
The average lightning current is about 20 000 A (or even greater), the lightning voltage is about 10 times 10 volts (the human body safety voltage of 36 volts), a lightning time is about one thousandth of a second, an average of a lightning issued by the power of 20 billion kilowatts (the general power of the rice cooker is less than 1,000 watts).
China's construction of the world's largest hydroelectric power plant - the Three Gorges hydroelectric power plant, the total installed capacity of the power plant is 18.2 million kilowatts, only one thousandth of a lightning power.
Of course the electrical power of lightning is very large, but because of the short discharge time, so the electrical power of the lightning current is not very large, once about 5555 degrees.
The world has more than 100 lightning phenomena per second, and the total electrical energy released by lightning in a year is about 1.75 billion kilowatts.
If one degree of electricity for 0.30 yuan, the world's annual value of lightning for 5.25 trillion yuan, which is a huge wealth, but due to the lightning time is very short, mankind has not been able to capture this power, the world has not yet studied the use of lightning power method.
The hazards of lightning
There are millions of lightning strikes in nature every year. Lightning is one of the ten most serious natural disasters declared by the United Nations International Decade for Disaster Reduction. The latest statistics show that the damage caused by lightning has risen to the third place of natural disasters. Every year, lightning strikes cause countless casualties and property losses around the world. According to incomplete statistics, China's annual lightning strikes as well as the negative effects of lightning strikes caused by casualties amounted to 3,000 to 4,000 people, property losses in the 5 billion to 10 billion yuan.
The scope of lightning disasters involved in almost all walks of life. One of the negative effects of the rapid development of modern electronic technology is the reduction of its ability to resist lightning surges. Large-scale integrated circuits as the core components of the measurement, monitoring, protection, communications, computer networks and other advanced electronic devices are widely used in electric power, aviation, defense, communications, broadcasting, finance, transportation, petrochemicals, medical care and other areas of modern life, large CMOS integrated components composed of these electronic devices generally exist on transient over-voltage, overcurrent tolerance ability is weak, transient over-voltage will not only cause the electronic equipment, but also the ability of overcurrent. Transient overvoltage will not only cause electronic equipment to produce misoperation, but also cause greater direct economic losses and a wide range of social impact.
There are four main hazards caused by lightning:
(1) direct hit mine
Charged clouds on the earth at a point where a violent discharge phenomenon, known as direct hit mine. Its destructive power is very huge, if it can not quickly diarrhea into the earth, will lead to discharge channel objects, buildings, facilities, people and animals suffered serious damage or damage - fire, building damage, destruction of electronic and electrical systems, and even endanger the lives of people and animals.
(2) lightning wave intrusion
Lightning is not directly discharged in the building and the equipment itself, but on the cables placed on the outside of the building discharge. Lightning wave or overvoltage on the cable spreads almost at the speed of light along the cable line, invading and endangering indoor electronic equipment and automation control and other systems. Therefore, often before hearing the sound of thunder, our electronic equipment, control systems, etc. may have been damaged.
(3) Induced overvoltage
Lightning strikes occur in the vicinity of equipment and facilities or lines, or lightning does not discharge directly to the ground, but only in the cloud to cloud discharge phenomenon. Lightning releases an electrical charge and generates an overvoltage inductively on power and data transmission lines and metal piping metal supports.
Lightning discharge in buildings with lightning facilities, lightning waves along the top of the building flashing device (lightning belt, lightning rod, lightning net or lightning rod), the process of lead wires leaked into the earth, will be in the lead wires around the formation of a strong transient magnetic field, the light is caused by the interference of electronic equipment, data loss, resulting in malfunctions or temporary paralysis; serious cases can cause components to break through and circuit boards In serious cases, it can cause the components to break down and circuit boards to burn, paralyzing the entire system.
(4) system internal operation overvoltage
Due to the operation of circuit breakers, heavy loads of electricity and inductive loads into and out of the system, system short-circuit faults and other changes in the internal state of the system parameters change, caused by the internal electromagnetic energy conversion of the power system, resulting in an internal overvoltage, that is, the operation of the overvoltage.
The amplitude of the operational overvoltage is small, but the probability of occurrence is much greater than the lightning induction overvoltage. Experiments have shown that both the induction overvoltage or internal operation overvoltage, are transient overvoltage (or transient overvoltage), and ultimately to the electrical surge of the way to jeopardize the electronic equipment, including the destruction of printed circuits printed lines, components and insulation premature aging life shortening, damage to the database or make the software malfunction, so that some of the control elements out of control.
(5) ground potential counterattack
If lightning strikes directly on a building or facility with lightning protection, the ground potential of the grounding network will be raised tens or hundreds of thousands of volts within a few microseconds. Highly destructive lightning current will flow from the grounded portion of various devices to the power supply system or various network signaling systems, or break through the earth's insulation and flow to the power supply system of another facility or various network signaling systems, thus counteracting the destruction or damage to electronic equipment. At the same time, the danger of spark discharge may be induced by high potentials in the wire circuits without equipotential connection.
Preventive techniques
1, the unit of lightning six ways
(1) units should be regularly qualified by the professional lightning detection agencies to test lightning protection facilities, to assess whether the lightning protection facilities in line with national norms.
(2) The unit should set up a person responsible for lightning disaster prevention, responsible for lightning safety work, the establishment of various lightning mitigation management regulations, the implementation of regular testing of lightning protection facilities, inspection after thunderstorms and routine maintenance.
(3) construction units in the design and construction of lightning protection facilities, should be based on geology, soil, meteorology, the environment, the characteristics of the protected object, the law of lightning activity and other factors for comprehensive consideration, the use of safe and reliable, technologically advanced, economically rational design and construction.
(4) should be used technology and quality are in line with national standards of lightning protection equipment, devices, equipment, to avoid the use of non-standard lightning protection products and devices.
(5) The new construction and new additions to the installation of equipment application of lightning protection system redesign and construction.
(6) lightning disaster should be reported to the City Lightning Protection Institute in a timely manner in order to deal with the situation in a timely manner to avoid another lightning strike.
2, personal lightning top ten tips
(1) should stay indoors and close the doors and windows; people working outdoors should hide in the building.
(2) You should not use TVs, stereos and other electrical appliances without lightning protection or with insufficient lightning protection, and you should not use water faucets.
(3) Do not touch the antenna, water pipes, barbed wire, metal doors and windows, building facades, and stay away from electric wires and other energized equipment or other similar metal devices.
(4) Reduce the use of telephones and mobile phones.
(5) Do not swim or engage in other water sports, should not play outdoor ball games, leave the water and other open space, looking for a place to hide.
(6) Do not stand on the top of a hill, on the roof of a building, or near other objects with high conductivity.
(7) Do not handle flammable materials in open containers.
(8) Stay away from trees and masts in the wilderness if you are unable to take shelter in a building with lightning protection.
(9) In the open field should not play umbrellas, should not be badminton, golf clubs, etc. on the shoulders.
(10) It is not advisable to drive a motorcycle or ride a bicycle.