Hello everyone, I'm Brother Xue. Lightning protection and grounding in the computer room is a very important work, which is focused on today.
The lightning protection and grounding system has always been the focus of attention in the data room, and the technology is becoming more and more mature. At present, the damage to equipment caused by lightning is more diverse, and the damage degree is more extensive and deep. Entering a new stage of development, the widespread application of microelectronic network equipment makes the problem of lightning protection more and more important. Due to the characteristics of high density, high speed, low voltage, and low power consumption, microelectronic devices are very sensitive to various electromagnetic interferences such as lightning overvoltage, power system operation overvoltage, electrostatic discharge, and electromagnetic radiation. If protection measures are not in place, you can suffer significant losses anytime, anywhere. It is worth our attention that lightning not only destroys the system equipment, but more importantly, it interrupts the communication of the system, stops the work, and damages the reputation, and its indirect losses are immeasurable.
The lightning protection and grounding system must carry out comprehensive defense from the perspective of the system, provide high-efficiency lightning connectors, safely guide the lightning current into the ground, improve the low-resistance ground grid, clear the ground circuit, and carry out power surge impact protection and signal and data line transient protection.
1. The principle of lightning protection and grounding system in the computer room
Grounding is the most important part of lightning protection technology, whether it is direct lightning, induction lightning or other forms of lightning, and finally the lightning current is sent to the earth. Therefore, lightning protection cannot be reliably avoided without a reasonable and good grounding device. The smaller the ground resistance, the faster the dispersion, the shorter the high potential holding time of the lightning object, and the less dangerous it is. Ohm is required for the grounding resistance of the computer site, and the common grounding method is adopted to unify the lightning protection grounding, electrical safety grounding, AC ground, and DC ground into one grounding device. If there is a special requirement to set up an independent place, it should be connected with a pole protector between the two networks, so that the two networks are usually independent to prevent interference, and when the lightning current comes, the two networks are instantly connected through the pole protector to form an equipotential connection.
2. The composition of the lightning protection and grounding system in the computer room
The lightning protection and grounding system is an important subsystem for the protection of weak current precision equipment and computer room, which is mainly composed of lightning receiving device, down conductor, grounding wire, grounding body (level), grounding device, grounding grid, and grounding resistance.
1. Lightning receiving device
Metal rods (lightning receivers) that directly or indirectly receive lightning, such as lightning rods, lightning belts (nets), overhead ground wires and lightning arresters.
2. Lead down
A conductor used to conduct lightning current from the lightning connector to the grounding device.
3. Grounding wire
A metal conductor that does not carry current under normal circumstances for the grounding terminal of electrical equipment and towers to be connected with the grounding body or neutral wire.
4. Grounding body (pole)
A metal conductor that is buried in the soil and is in direct contact with the earth is called a grounding body. It is divided into vertical ground body and horizontal grounding body.
5, Grounding device
A general term for grounding wires and grounding bodies.
6. a grounding grid
A mesh grounding device composed of vertical and horizontal grounding bodies with the effect of discharge and pressure equalization.
7. Ground resistance
The sum of the grounding resistance of the grounding body or the natural grounding body is called the grounding resistance of the grounding device, and its value is equal to the ratio of the grounding voltage of the grounding device to the current flowing into the ground through the grounding body. At the same time, the grounding resistance is also a sign to measure the level of the grounding device.
3. Lightning protection design of the computer room
Due to the large number of protection points and wide coverage of the network integration system, in order to protect the building and the electronic network equipment in each direction in the building from lightning damage or minimize the lightning damage, the lightning protection scheme should be designed from the perspective of overall lightning protection. At present, comprehensive lightning protection is adopted, and the comprehensive lightning protection design scheme should include two aspects: the protection of direct lightning and the protection of induction mines, and the lack of any one aspect is incomplete, defective and potentially dangerous. At the same time, lightning protection is mainly carried out from two aspects: power supply and signal system.
1. Protection against direct lightning
If there is no direct lightning protection, according to the IEC1312 estimate, almost all lightning currents flow through the conductor type line (such as power line, signal line, etc.) in and out of the building to invade the equipment, so the damage is very serious, so do a good job of direct lightning protection is the premise of induction lightning protection; direct lightning protection is designed and constructed in accordance with the national standard GB50057 "building lightning protection design code", mainly using lightning rods, nets, wires, With a good grounding system, the purpose of which is to protect the exterior of the building from lightning strikes and provide a relatively safe environment for people or equipment in the building.
2. Protection of power supply system
Statistics show that more than 80% of lightning accidents in microelectronic network systems are caused by lightning impulse overvoltages induced on the power lines connected to the system. Therefore, the protection of the power cord is a part that cannot be ignored in the overall lightning protection.
3. Protection of signal system
Although lightning protection devices are installed on external incoming lines such as power supply and communication lines, lightning strikes occur in network cables (such as twisted pair cables) and induce overvoltage, which will still affect the normal operation of the network and even completely destroy the network system. In addition, when the power line or communication line transmits the lightning strike voltage, or the ground wire system of the building is discharged from the lightning strike, the strong transient current is generated, and the overvoltage induced by the network transmission line is enough to destroy the network at one time. Even if it is not a particularly high overvoltage, it cannot destroy the equipment at one time, but every overvoltage impact accelerates the aging of network equipment, affects the transmission and storage of data, and even crashes until it is completely damaged. Therefore, the defense of the network signal line is for the overall defense of the network integration system. It is a very important link.
4. Equipotential connection
The central computer room where the backbone switch of the integrated network system is located shall be provided with a pressure equalizing ring to electrically connect all metal objects in the computer room, including cable shields, metal pipes, metal doors and windows, equipment shells, and all metal pipes entering and exiting the building, and connect them to the voltage equalizing ring to equalize the potential.
5, Grounding
The use of joint grounding in the computer room can effectively solve the influence of the increase of ground potential, and the qualified ground grid is the key to effective lightning protection. The joint ground grid of the computer room is usually composed of the building foundation (including ground piles), the annular grounding (body) device, and the working (power transformer) ground grid. For the lightning protection of sensitive data communication equipment, the quality of the grounding system is directly related to the effect and quality of lightning protection. If the ground network does not meet the requirements, the ground network conditions should be improved, the area of the ground network should be appropriately expanded, and the structure of the ground network should be improved, so that the lightning current can be discharged as soon as possible, and the holding time of high overvoltage caused by the lightning current should be shortened. to meet the lightning protection requirements.
A. Power lightning protection
The lightning protection of the power system adopts the method of three-level lightning protection. The lightning protection of the distribution box of the computer room should be not less than two levels of protection (fine protection), that is, the input of the main distribution box of the computer room is installed with a secondary lightning protector, and the output of the distribution box of the computer room is installed with a three-level lightning protector. That is, the secondary lightning protector is installed at the front end of the main switch in the distribution cabinet, which not only saves space, but also plays the role of beauty and easy maintenance, and installs the three-level lightning protector at the front end of the main switch of the mains distribution cabinet and UPS distribution cabinet respectively to protect the equipment in the computer room.
B. Lightning protection of the signaling system
(1) The network transmission line mainly uses optical fiber and twisted pair. The optical fiber does not require special lightning protection measures, but if the outdoor optical fiber is overhead, then the metal part of the optical fiber needs to be grounded. The shielding effect of twisted pair wire is poor, so the possibility of inducing lightning strike is relatively large, this kind of signal wire should be laid in the shielded trunking, and the shielded trunking should be well grounded;
(2) The installation of signal lightning protection on the signal line is an effective way to prevent induction lightning. For the network integration system, a special signal lightning protector can be installed before the network signal line enters the WAN router, and a signal anti-rich device with RJ45 interface can be installed at the entrance of the signal line of the backbone switch, the main server and each branch switch and server of the system. The selection of signal lightning protection device should comprehensively consider the working voltage, transmission rate, interface form, etc. The arrester is mainly connected in series at the interface of the equipment at both ends of the line.
a. A single-port RJ45 port signal arrester is installed at the 100M input port of the server to protect the server.
b.24-port network switch series 24-port RJ45 port signal arrester to avoid damage to equipment due to lightning induction or electromagnetic field interference along the twisted pair.
c. Install a single-port RJ11 port signal arrester on the receiving equipment of the DDN private line to protect the equipment on the DDN private line.
d. Install a coaxial port antenna feeder arrester at the front end of the satellite receiving equipment to protect the receiving equipment.
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