There are millions of lightning strikes in nature every year, and lightning disasters are one of the ten most serious natural disasters announced by the United Nations International Decade for Disaster Reduction. The latest statistics show that the losses caused by lightning have risen to the third place among natural disasters. Lightning strikes cause countless casualties and property losses around the world every year. According to incomplete statistics, there are 3,000 to 4,000 casualties in my country every year due to lightning strikes and negative effects of lightning strikes, and property losses range from 5 billion to 10 billion yuan.
Thunder and lightning disasters involve almost all walks of life. One of the negative effects brought about by the rapid development of modern electronic technology is the reduction of its ability to withstand lightning surges. Advanced electronic equipment such as measurement, monitoring, protection, communication, and computer networks with large-scale integrated circuits as core components are widely used in electric power, aviation, national defense, communications, radio and television, finance, transportation, petrochemicals, medical care, and other fields of modern life. , these electronic devices composed of large CMOS integrated components generally have the disadvantage of weak tolerance to transient overvoltage and overcurrent. Transient overvoltage will not only cause malfunction of electronic equipment, but also cause greater direct damage. economic losses and widespread social impacts. Direct lightning
The violent discharge phenomenon caused by charged clouds on a certain point on the earth is called direct lightning. Its destructive power is very huge. If it cannot be discharged into the earth quickly, it will cause serious damage or damage to objects, buildings, facilities, people and animals in the discharge channel - fire, damage to buildings, destruction of electronic and electrical systems, It may even endanger the lives of humans and animals.
Lightning wave intrusion
Lightning does not discharge directly on the building and equipment itself, but on the cables laid outside the building. Lightning waves or overvoltages on cables spread along the cable lines almost at the speed of light, invading and endangering various systems such as indoor electronic equipment and automation control. Therefore, often before hearing thunder, our electronic equipment, control systems, etc. may have been damaged.
Induced overvoltage
Lightning strikes occur near equipment, facilities or lines, or lightning does not discharge directly to the ground, but only discharges between clouds. Lightning releases electrical charges and induces overvoltages in power and data transmission lines and metal supports on metal pipes.
When lightning discharges to a building with lightning protection facilities, the lightning wave is discharged to the earth along the air terminal (lightning protection belt, lightning protection wire, lightning protection net or lightning rod) and down conductor on the top of the building. , a strong transient magnetic field will be formed around the down conductor, which may cause interference to electronic equipment, loss of data, malfunction or temporary paralysis; in serious cases, it may cause component breakdown and circuit board burnout, causing the entire system to collapse. paralysis.
System internal operating overvoltage
System parameters may occur due to changes in the internal state of the system such as the operation of circuit breakers, the input and removal of heavy power loads and inductive loads, system short-circuit faults, etc. Changes cause the transformation of electromagnetic energy inside the power system, resulting in internal overvoltage, that is, operating overvoltage.
Although the amplitude of operating overvoltage is small, the probability of occurrence is much greater than lightning induced overvoltage. Experiments have proven that whether it is induced overvoltage or internal operating overvoltage, it is a transient overvoltage (or instantaneous overvoltage), which ultimately endangers electronic equipment in the form of electrical surges, including damaging printed circuit traces, components and insulation. Premature aging shortens the service life, damages the database or causes software misoperation, causing some control components to go out of control.
Ground potential counterattack
If lightning directly hits a building or facility with a lightning protection device, the ground potential of the grounding grid will be raised by tens of thousands or tens of thousands in a few microseconds. One hundred thousand volts. Highly destructive lightning current will flow from the grounded part of various devices to the power supply system or various network signal systems, or it will break down the earth insulation and flow to the power supply system of another facility or various network signal systems, thereby counterattacking damage or damage electronic equipment. At the same time, in wire circuits where equipotential bonding is not implemented, high potential may be induced, resulting in the risk of spark discharge.