Ways of lightning invasion.
Usually the so-called lightning strike refers to a part of the cloud that is charged and another part of the cloud that is charged with a different type of charge, or the charged cloud that rapidly discharges electricity to the earth. This rapid discharge process produces intense lightning and loud sounds. Of course, the discharge between clouds is mainly harmful to aircraft and has little impact on buildings, people and animals on the ground. However, the discharge of clouds to the earth is very harmful to buildings, electronic and electrical equipment, people and animals.
Because lightning strikes can bring disaster to humans, humans have been fighting against lightning strikes for a long time. In the middle of the 18th century in China, the famous scientist Frank Frank (F Sov Lomonsov JJMOMOC) was famous as Mrank (XLOIAMMH). They established the lightning theory through a large number of experiments and believed that lightning strikes are the phenomenon of rapid neutralization of a large number of yin and yang charges in the cloud; they also created the lightning protection theory and invented the lightning rod. These scientific achievements have made great contributions to mankind.
In ancient Chinese books, lightning arrester manufacturers have rich records of lightning theory and lightning protection practices. For example, "Zhuangzi" said in the Eastern Zhou Dynasty: Yin and Yang are divided into electricity, and the intersection of Yang and Yin is thunder. Yin and Yang go wrongly, and the heaven and earth are shaken, so there is thunder. These theories are so similar to modern thunder and lightning theory, but predate it by more than 2,000 years. There are also rich records of lightning protection in construction projects in ancient books. There is the following record in Meng Ao's "Northern Expedition" of the Southern and Northern Dynasties: A hundred steps away from the south corner of Lingyuntai, there is a white stone room called the lightning protection room. There is also a record in Sheng Xianzhi's "Jingzhou Ji": In the spring and Autumn period of the Liao Dynasty in Huyang County, Fan Zhong's mother was afraid of thunder, so she built a stone room to avoid it. The aragonite was used as a step, which still exists today. According to analysis, the white stone and aragonite mentioned in the book should be stones with good insulation properties. As for the buildings in the Song, Yuan, Ming and Qing dynasties, most of them adopted lightning protection measures such as thunder pillars (called Chengzhu in the Song Dynasty).
Lightning classification
Generally speaking, lightning can be roughly divided into direct lightning and induction lightning. Direct lightning is extremely harmful. Any communication equipment directly hit by direct lightning will be damaged. Induction lightning means that when lightning discharges, electrostatic induction and electromagnetic induction will be generated on nearby conductors. The general way lightning invades a data room is as follows:
1. Direct lightning strike, the overhead cable is struck by lightning, and part of the lightning current enters the computer room along the cable.
2. Induction of lightning: Lightning electromagnetic pulses are inductively coupled to outdoor cables, generating high-voltage lightning currents that invade the computer room along the cables, causing malfunctions in the computer room.
3. Direct lightning strikes, ground potential counterattack, lightning current leaks along the ground wire, causing a large voltage drop on the ground wire, and the ground potential difference in the equipment room causes equipment failure. 4. The inductive coupling of lightning and lightning electromagnetic pulses to indoor loops forms induced currents on indoor cables, causing harm to equipment.
Ways of lightning invasion.
1. Direct lightning strike means that lightning directly hits a building, producing electrical effects, thermal effects and mechanical forces, causing damage to the building. After a direct lightning strike on a building, a strong lightning strike current leads down the wire along the ground. After the grounding body enters the ground, the ground potential will immediately rise, generating a high potential, causing ground potential to counterattack, damaging equipment or causing casualties.
2. Lightning induction means that when lightning discharges, electrostatic induction and electromagnetic induction are generated on nearby conductors, which can produce sparks between metal parts. Lightning induction can come from landmines or cloud discharges. Because the mine is close to the lightning strike point, the induced surge voltage is large and the radius of action is large. Generally speaking, electronic information equipment within a range of 500 meters is the target of damage; although the induced surge voltage of cloud discharge is small, the probability of occurrence is high. Electrostatic induction is due to the action of the thundercloud leader, which causes nearby conductors to sense charges with opposite signs to the leader channel. When the thundercloud main discharges, the charge in the leading channel is quickly neutralized, and the induced charge on the conductor is released. If there is no nearby leakage to the ground, a very high electrical potential will develop. Electromagnetic induction is a transient strong electromagnetic field produced by the rapid change of current in the surrounding space, causing nearby conductors to generate high electromotive force.
3. The intrusion of lightning waves is due to the effect of lightning on overhead lines or metal pipes. Lightning waves may invade indoors along these pipes, endangering personal safety and damaging equipment. According to lightning electromagnetic pulse protection theory and practical experience, the main cause of damage to electronic information equipment is lightning-induced surge voltage. Induced surge voltage waves can be introduced into electronic information equipment through various leads, damaging their chips and interfaces.
Data centers attach great importance to the continuity of power supply, so lightning protection cannot be ignored. Network equipment with excellent performance itself has lightning protection function. On the power supply lines, there are line designs to absorb high-voltage surges. Although the product has lightning protection function, the induced voltage generated by lightning is several thousand volts, tens of thousands volts or even higher. Regardless of the brand of router, the lightning protection function of the router itself can only solve some of the hazards caused by lightning. In order to further reduce the harm caused by lightning, corresponding lightning protection equipment must be equipped.
Lightning protection measures
1. An independent lightning rod or overhead lightning protection wire should be installed. Protected buildings, hoods, radiator pipes and other objects protruding from the roof are within the protection range of the air terminal. Metal oxide arresters use lightning rods, lightning protection belts and lightning protection nets to safely flow lightning current into the earth along down conductors to prevent lightning from directly hitting buildings and equipment.
2. The following spaces outside the openings of discharge pipes, breathing valves, exhaust pipes, etc. that discharge explosive hazardous gases, steam or dust should be within the protection range of the air-termination device.
3. For towers with independent lightning rods, at least one down conductor should be provided at the end of the overhead lightning protection wire and each column of the overhead lightning protection network. Made of metal or welded, the towers and columns connected to the steel bars are tied and used as lower leads.
4. Independent lightning rods and independent grounding devices for overhead lightning protection lines. The impact grounding resistance of each down-conductor shall not be greater than 10Ω. In areas with high soil resistivity, the impact ground resistance can be appropriately increased.
5. Shield all metal wires in computer systems, including power cables. Communication cables and signal lines are shielded with shielded wires or metal tubes. During the construction of the computer room, metal materials such as construction steel mesh are used to form a shielding cage. Prevent external electromagnetic waves (including lightning electromagnetic waves and electrostatic induction) from interfering with computer room equipment.
6. When trees are higher than buildings and are not within the flash protection range, the clear distance between trees and buildings should not be less than 5cm.
7. The positional relationship between the lightning protection system and these pipes must be considered in the lightning protection design for signal lines for lighting, power, telephone, network and various computer equipment. Therefore, reasonable wiring is one of the important factors in lightning protection design.
In addition, corresponding overvoltage protectors should be installed on the signal lines of electronic equipment to use their nonlinear effects to filter excessive pulse voltages on the lines to protect equipment from overvoltage damage. The main protection devices are zinc oxide varistors, diode or triode discharge tubes, fast clamping diodes, etc. They can be combined as needed to form a complete lightning protector.
Data center equipment protection.
1. Protect from direct lightning strikes.
If there is no direct lightning protection, almost all lightning current will flow through the wires entering and leaving the building (power wires, signal wires, etc.), causing serious damage. Therefore, direct lightning strike protection is the prerequisite for induction lightning strike protection; direct lightning strike protection is designed and constructed in accordance with the national standard GB50057 "Building Lightning Protection Design Code" and mainly uses lightning rods, networks, lines and good grounding systems. The purpose is to protect buildings from lightning strikes and provide a relatively safe environment for people or equipment in the building.
2. Protect the power system.
Statistics show that more than 80% of lightning accidents in microelectronic network systems are caused by lightning impulse overvoltage induced on the power supply lines connected to the system. Therefore, protecting power lines is an integral part of overall lightning protection that cannot be ignored.
3. Protect the signaling system.
Although lightning protection devices are installed on external introduction lines such as power supply and communication lines, due to overvoltage induced in network lines (such as twisted pairs), lightning strikes from high-voltage arresters will still affect the normal operation of the network, or even completely destroy the network system. A huge transient magnetic field is generated during a lightning strike. Metal rings within 1 kilometer, such as network metal connections, will feel strong induced lightning strikes; in addition, when power lines or communication lines transmit lightning strike voltage, or building ground wire systems generate strong transient currents. For network transmission lines, the induced overvoltage is enough to destroy the network in one go. Even if the overvoltage is not particularly high, it cannot damage the equipment at once, but each overvoltage impact will accelerate the aging of network equipment, affect data transmission and storage, and even DOWN the machine until it is completely damaged. Therefore, the lightning protection of network signal lines is an important part of the overall lightning protection of the network integrated system.
