Voltage cable branch box has no lightning impact test

The phenomenon of lightning strikes usually refers to the direct lightning metal body (including flashover, grounding lead and grounding body), in the instant of flashover and the earth between the existence of a very high voltage, this voltage and the earth connected to the other metal objects discharge (also known as flashover) phenomenon is called a counterstrike. In addition, when lightning strikes a tree, the high voltage on the tree and its neighboring houses, metal objects will also occur between the backlash. To eliminate the phenomenon of counterstrike, two measures are usually taken: one is to make an equipotential connection, using a metal conductor to connect the two metal conductors, so that their potentials are equal at the time of the flashover; the second is to maintain a certain distance between the two. Comprehensive anti-lightning countermeasures modern lightning protection including external lightning protection (buildings or facilities of direct lightning protection) and internal lightning protection (lightning electromagnetic pulse protection) two parts, the external lightning protection system is mainly to protect the building from direct lightning caused by fire accidents and personal safety accidents, while the internal lightning protection system is to prevent the intrusion of lightning waves, lightning induced over-voltage and over-voltage of the operation of the system The internal lightning protection system is to prevent lightning wave intrusion, lightning induction overvoltage and system operation overvoltage invasion of equipment caused by the destruction, which can not be guaranteed by external lightning protection system. Lightning is a very complex issue, it is not possible to rely on one or two kinds of advanced lightning protection equipment and lightning protection measures can completely eliminate the impact of lightning overvoltage and induced overvoltage, must be directed at lightning intrusion path, the various types of factors that may produce lightning strikes to be excluded, the use of integrated prevention and control - flashover, equalization, shielding, grounding, shunt (protection), in order to reduce lightning damage. Protection), in order to reduce lightning damage to a minimum. 1, flashover flashing device is what we often say lightning rod, lightning belt, lightning rod or lightning net, flashover is to allow a certain degree of range of lightning discharges can not arbitrarily select the discharge channel, but only in accordance with the pre-design of the people of the lightning protection system of the prescribed channel, the lightning energy will be leaked to the earth. 2, equalizing pressure flashing device in the lightning, the lead line immediately generate high potential. Lead wire immediately produce high potential, will be around the lightning protection system is still in the ground potential of the conductor to produce side flashover, and make its potential rise, and then on the personnel and equipment constitute a hazard. In order to reduce this flashover hazard, the simplest method is to use a voltage equalizing ring to equipotentially connect conductors at ground potential all the way to the grounding device. Indoor metal installations, electrical installations and electronic equipment should be equipotentially connected to the lightning protection system with thicker conductors if their distance from the conductors of the lightning protection system, in particular the flashover, does not meet the specified safety requirements. So that in the lightning current through, all the indoor facilities immediately form an "equipotential island", to ensure that the conductive components do not produce harmful potential difference between the side of the flashover discharge does not occur. Perfect equipotential connection can also prevent the lightning current into the ground caused by the ground potential rise generated by the counterattack. In order to completely eliminate the destructive potential difference caused by lightning, it is especially necessary to implement the equipotential connection, power lines, signal lines, metal piping, etc. should be through the overvoltage protector for equipotential connection, the interface of each inner layer of the protection zone should be the same according to the local equipotential connection, and finally connected with the equipotential connection bus bar. 3, shielding shielding is the use of metal nets, foils, shells, or tubes, and other conductors need to be protected. The object is surrounded, so that lightning electromagnetic pulse wave invasion channel all cut off. All shielding sets, shells, etc. need to be grounded. Shielding is the most effective way to prevent the impact of lightning electromagnetic pulse radiation on electronic equipment. 4, grounding is to have been within the lightning protection system of lightning current flows smoothly into the earth, and can not let the lightning energy is concentrated in the lightning protection system somewhere on the protected object to produce damage, good grounding in order to effectively discharge the lightning energy, reduce the voltage on the lead line to avoid the occurrence of counterattacks. In the past, some specifications require electronic equipment separately grounded, the purpose is to prevent stray currents in the grid or transient current interference with the normal operation of the equipment. 90 years ago, the force's communication and navigation equipment to electronic tube devices, the use of analog communication, analog communication is particularly sensitive to interference, in order to anti-interference, so they are to take the power supply and communication grounding separate method. Now, the field of lightning protection engineering does not advocate separate grounding. In the IEC standards and ITU standards do not advocate separate grounding, the U.S. standard IEEEStd1100-1992 pointed out more pointedly: it is not recommended to use any kind of so-called separate, independent, computer, electronic or other such incorrect earth grounding as a connection point of the grounding conductor of the equipment. Lightning protection grounding is the most basic part of the lightning protection system, but also the most basic safety requirements in the lightning protection installation acceptance specification. Grounding is not good, all the lightning protection measures can not play out the effect of lightning protection. 5, shunt (protection) which is the focus of the rapid development of modern lightning protection technology, is to protect a variety of electronic equipment or electrical systems, the key measures. The so-called shunt is in all from outdoor conductors (including electric power lines, data lines, telephone lines or antenna feeder lines and other signal lines) and lightning grounding devices or grounding lines are connected in parallel with an appropriate lightning arrester SPD, when a direct lightning strike or lightning effect on the line generated by the overvoltage wave along the conductor into the room or the equipment, the arrester's resistance suddenly dropped to a low value, nearly short-circuit state, the lightning current will be thus Branch into the ground. Lightning current in the shunt, there will still be a small part along the wire into the equipment, which is not resistant to some high-voltage microelectronic equipment is very dangerous, so for this type of equipment in the wire into the chassis before the multi-level shunt should be carried out (i.e., not less than three levels of lightning protection). Now the lightning arrester research and development, but also beyond the scope of shunt. Some lightning arrester can be directly connected in series in the signal line or antenna feeder, they can let the useful signal through smoothly, and the lightning overvoltage wave blocking. When using the shunt as a lightning protection measure, special attention should be paid to the selection of the performance parameters of the lightning arrester, because the installation of additional facilities will affect the performance of the system to a greater or lesser extent. For example, the signal arrester access should not affect the system transmission rate; antenna feed arrester in the passband loss should be as small as possible; if used in directional equipment, can not lead to positioning errors. 6, avoid in the building infrastructure siting, it should be avoided in the lightning area or lightning prone locations, so as not to increase the expenditure and cost of lightning protection works in future. When lightning occurs, turn off the equipment and unplug the power supply. Network room lightning protection design 2007-05-0107:07 Currently, with the rapid development of computer and network communications technology, computer network systems for lightning protection requirements are increasingly high, due to the lightning protection measures are not effective or there is a bias in the understanding of the protective effect often does not play a due protective effect, the room suffered a frequent occurrence of lightning strikes. Especially in the season of thunderstorms, computer network systems, some of the electrical and electronic equipment by the interference of lightning, some of the lightning and burned, resulting in direct economic losses. Lightning protection of computer network systems should pay enough attention to be prepared, the lightning protection facilities to rectify, do a good job of the overall protection measures, in order to better maintain the safe operation of the server room. Second, the solution 1.1 building direct lightning protection in accordance with national standards GB50057-94 "Building Lightning Protection Design Code," the requirements of the important computer network system room where the building for the second or third type of lightning protection buildings, generally in accordance with the requirements of the construction of lightning facilities, such as the building's sky lightning net (with), lightning rods or a mixture of lightning catcher, etc., which is a lightning catcher through the building columns The main steel reinforcement of the foundation, the powerful lightning current into the earth, forming a better building lightning protection facilities. Computer system set up in the building, protected by the building lightning protection system, the possibility of direct lightning directly hit the computer network system is very small, so usually do not have to install the equipment to protect the direct lightning.1.2 Computer network system induced lightning protection induced lightning generated by electrostatic induction, but also by electromagnetic induction, the formation of induced lightning voltage is very high, the building of low-voltage electronic equipment to cause a greater threat, the computer network system protection against lightning. The threat of computer network system lightning protection focuses on the prevention of induced lightning invasion. Invasion of computer systems, lightning overvoltage overcurrent mainly the following three ways: (1) by the AC power supply line invasion of computer systems power supply from outdoor overhead power lines into the room, overhead power lines may be subjected to direct lightning and induced lightning; direct lightning strikes in the high-voltage power lines, through the transformer coupled to the 380V low-voltage side, invasion of the computer power supply equipment; in addition to the low-voltage lines may be a direct strike! lightning or induction of lightning overvoltage. Lightning overvoltage in the 220V power line on average up to 10,000V, the computer network system can cause devastation. (2) by the computer communication line invasion by the computer communication line invasion is divided into three cases. Situation one: when the ground protrudes by direct lightning strikes, strong lightning voltage will be adjacent to the soil breakthrough, lightning current directly invades the cable outer skin, and then break through the outer skin, so that high-voltage intrusion lines. Situation 2: When a thundercloud discharges on the ground, it induces an overvoltage of thousands of volts on the line, destroying the electrical equipment connected to the line, and intruding into the communication line through the equipment connecting lines. This intrusion spreads along the communication line, involving a wide range of hazards. Situation 3: If through a multi-core cable connected to different sources of conductors or multiple cables laid in parallel, when a conductor is struck by lightning, it will be in the neighboring wires induced over-voltage, knocking down low-voltage electronic equipment. (3) ground potential counterattack voltage through the grounding body invasion of lightning when a strong lightning current through the lead and grounding body leaked into the earth, in the vicinity of the grounding body radial potential distribution, if there are connected to other electronic equipment grounding close to, that is, to produce high-voltage ground potential counterattack, the invasion voltage can be as high as tens of thousands of volts. Building lightning protection against direct lightning introduced a strong lightning current through the lead line into the ground, in the vicinity of the space to produce a strong electromagnetic field changes will be induced in the adjacent wires (including power lines and signal lines) on the lightning overvoltage, so the building lightning protection system is not only unable to protect the computer system, but may be introduced to the lightning current. Computer network systems and other equipment such as integrated circuit chip voltage resistance is very weak, usually below 100V, so it is necessary to establish a multi-level computer lightning protection system, layer by layer protection, to ensure the safety of the computer network system.2. Solution (1) for the impact of the lightning electromagnetic field, mainly when a direct lightning strike in the computer room building, the lightning current in the internal distribution of the building directly affects computer network system Equipment, especially for electromagnetic interference sensitive computer and network communication terminal equipment. Reasonable selection of the location of the server room and server room equipment can effectively reduce the reasonable layout of lightning damage. (2) Installing surge protectors SPD at the interface of power supply system and computer network terminal equipment, and taking measures such as shielding, grounding, and realizing equipotential connection for cables in and out of the computer room can effectively reduce the infringement of lightning over-voltage on the computer network system equipment. (3) computer room using joint grounding can effectively solve the impact of rising ground potential, qualified ground network is the key to effective lightning protection. The joint ground network of the computer room is usually composed of the foundation of the computer room building (including ground piles), ring-type grounding (body) device, work (power transformer) ground network and so on. For lightning protection of sensitive data communication equipment, whether the grounding system is good or not is directly related to the effect and quality of lightning protection. If the ground network is not required, should improve the conditions of the ground network, properly expand the area of the ground network and improve the structure of the ground network, so that the lightning current is discharged as soon as possible to shorten the lightning current caused by the high over-voltage retention time, in order to achieve the lightning protection requirements. Third, examples of 1. Basic situation of a company's computer room, in the company's building on the third floor, the building has a lightning rod, lightning belt and other external lightning protection facilities; computer network system power supply system from the utility three-phase low-voltage power supply, power supply room power supply from the distribution room switchboard straight for the building distribution box, from the building distribution box to the power distribution box to supply the room UPS power supply equipment; computer network communication lines in and out of the computer room using the UTP Twisted-pair cable, communication line line using voice cable line, satellite feeder using BNC interface coaxial cable; machine room grounding using the building grounding network. 2. program design machine room where the building has a lightning rod, lightning rod, lightning belt and other external lightning facilities, no longer external lightning supplementary design. Computer network system lightning electromagnetic pulse protection is designed according to the requirements of Class A, the power supply system to take 3 ~ 4 level surge protector (SPD) (hereinafter referred to as lightning arrester) for protection. The network communication system adopts fine protection, and for the cables and wires entering and leaving the protected area, signal interface surge protectors (SPD) are appropriately installed when entering the protected area. The machine room implements joint grounding, establishes qualified grounding system, and implements equipotential connection for pipes, wires and troughs entering and leaving the interface of the protection area. Effectively reduce the lightning overvoltage to a level that the equipment can withstand. Design content mainly includes: (1) machine room equipment transient overvoltage protection design; (2) machine room equipotential connection design; (3) grounding network production design. 3. machine room power supply equipment transient overvoltage protection computer network room as a desire to protect the region, from the EMC (electromagnetic compatibility) point of view, from outside to inside can be divided into several levels of protection zone. Outside the building building is the area of direct lightning, the equipment in this area is most likely to suffer damage, the highest risk, is the exposed area, for the 0 area; the building is located in the interior to the machine room for the non-exposed area, which can be divided into 1 area, 2 areas, the more to the interior, the lower the degree of danger. Power lines are one of the main ways of lightning overvoltage intrusion. From the main distribution room transformer low-voltage output to the equipment side of the room, must implement graded protection, lightning overvoltage reduced to the level of equipment can withstand.3.1 power supply lightning arrester configuration (1) the total low-voltage distribution room of the total power distribution cabinet power output configuration three-phase box-type power supply arrester 1, as the first level of lightning protection. Nominal discharge current selection 50 ~ 100kA, to prevent direct lightning. (2) The network equipment is located in the building floor main distribution box power supply into the end of the configuration box-type power lightning arrester, as the second level of lightning protection. Configuration of three-phase box-type lightning arrester, nominal discharge current selection of 40kA, to prevent induced lightning or operational overvoltage. (3) Network equipment room power distribution box power supply into the end of the configuration of power lightning arrester, as the third level of lightning protection. Configuration of single-phase box-type lightning arrester, nominal discharge current selection of 20kA, to prevent induced lightning strikes or operational overvoltage. (4) Important network cabinets or equipment using modular power arrester, as the fourth level of lightning protection. Nominal discharge current selection of 5kA, to prevent induced lightning or operational overvoltage.3.2 Data (signal) communication interface lightning arrester configuration according to the specific circumstances of the communication equipment, mainly considered by the outdoor introduction of data (voice) or video signal line lightning protection. Lightning arrester is mainly strung on the line at both ends of the interface of the equipment. (1) A single RJ45 port signal lightning arrester is installed at the 100M input port of the server to protect the server. (2) 24-port network switches are connected in series with 24-port RJ45 port signal lightning arrester to avoid the destruction of equipment due to lightning induction or electromagnetic field interference along the twisted-pair cable. (3) Install a single RJ11 port signal lightning arrester on the DDN leased line receiving equipment to protect the equipment on the DDN leased line. (4) in the satellite receiving equipment front-end installation of coaxial port antenna lightning arrester to protect the receiving equipment.4. Equipotential connection design in the room to do a total grounding manifold, so that the AC grounding, safety and protective grounding, DC grounding, lightning grounding, and other four kinds of grounding **** with a group of grounding devices. Machine room grounding manifold as far as possible installed in the anti-static floor under the hidden place. Shield all communication cables and cables entering the building with metal piping, and ground all metal piping (including water pipes, gas pipes, and various shielded piping) close to the building before entering it. The use of joint grounding network, the purpose is to eliminate the potential difference between the various networks, to ensure that the equipment is not damaged due to lightning backlash.5. Grounding network production design grounding is one of the very important aspects of lightning technology, either direct lightning or induction lightning, the ultimate is to introduce the lightning current into the earth. Therefore, for sensitive data (signal) communication equipment, there is no reasonable and good grounding system is not reliable lightning. Therefore, the grounding resistance >1Ω of the building ground network, need to be rectified in accordance with the specification requirements, in order to improve the reliability of the machine room grounding system. According to the specific circumstances, through the machine room building along the establishment of different forms of grounding network (including horizontal grounding body, vertical grounding body) to expand the effective area of the grounding network and improve the structure of the ground network. The basic requirements are as follows: (1) make the grounding network around the building to complete the most effective grounding device with less material and lower installation cost; (1) the grounding resistance value requires R < 1Ω; (2) the grounding body should be set about 3-5m away from the main building where the machine room is located; (3) the horizontal and vertical grounding body should be buried in the ground for about 0.8m, and the vertical grounding body should be 2.5m long, and set up every 3-5m of the Vertical grounding body; (4) vertical grounding body using 50 × 50 × 5mm hot-dip galvanized steel angle, horizontal grounding body is selected 50 × 5mm hot-dip galvanized flat steel; (5) in the ground mesh welding, the welded area should be ≥ 6 times the point of contact, and welded joints to do anti-corrosion and anti-rust treatment; (6) around the ground mesh should be in the ground at 0.6-0.8m below the ground with a number of building columns rebar welded and made anti-corrosion and anti-rust treatment; ( (7) poor soil conductivity using the laying of reducing agent method, so that the grounding resistance ≤ 1 Ω; (8) backfill soil must be a good conductive state of the new clay; (9) and the building foundation ground network multi-point welding, and reserved grounding test points. The above is a traditional cheap and practical grounding methods, according to the actual situation, grounding network materials can also choose new technology grounding devices, such as maintenance-free electrolytic ion grounding system, low resistance grounding module, long-lasting copper-clad steel grounding rod and so on. Fourth, the conclusion of the computer network system of lightning overvoltage protection requirements are relatively high, the computer network system for lightning protection design, should be based on the geographic environment where the server room for comprehensive consideration, after a reasonable lightning risk analysis, for the main source of lightning invasion of equipment in the server room, the overall protection, and according to the existing experience of a number of mature lightning protection technology, to take cost-effective protective measures. Safeguard the safe and stable operation of computer network system equipment. I hope you can help, huh