When fasteners are used for connection, the joint shall be tinned
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The layout of communication cable trunking and ground wire trunking shall not be close to the building column or beam as far as possible, and keep a long distance from it
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The design of communication cable trunking and ground wire trunking shall be far away from the building column or beam as far as possible
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Requirements for the wiring and grounding mode of communication network system in the building: the layout of communication cables and ground wires should be concentrated in the middle of the building as far as possible
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Therefore, in the design of artificial grounding body, it should be based on the soil resistivity, soil distribution and other geological conditions where the grounding grid is located
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1、 What is lightning protection grounding? Lightning protection grounding is divided into two concepts, one is lightning protection, to prevent damage caused by lightning; the other is grounding, to ensure the normal work of electrical equipment and personal safety
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4、 When the construction method of grounding device in communication machine room is divided into safety protection grounding, DC working grounding and lightning protection grounding, the grounding resistance value shall meet the following requirements: ① safety protection grounding, the grounding resistance shall not be more than 10 Ω; ② DC working grounding, the grounding resistance shall not be more than 4 Ω; ③ lightning protection grounding, the grounding resistance shall not be more than 10 Ω.
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When adopting combined grounding system, the following requirements shall be met: ① joint grounding body, protective grounding body, lightning protection grounding body of house, metal outer sheath of underground cable, concrete electrode and metal water pipe shall be connected into a grounding system, and fusion welding and anti-corrosion measures shall be taken; ② underground cable lead-in mode shall be adopted for all communication lines, and lightning protection equipment shall be installed; ③ The metal part of indoor communication equipment shall not be used to form the discharge channel of lightning current
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It is not feasible to design the grounding project without the specific situation of the project location
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③ The space distance between the outdoor lead wire of the grounding system and the lightning discharge line of the house: when the height of the house is 30m or below, it should be more than 2m generally
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As a conductor which is in close contact with the earth and provides electrical connection with the earth, the grounding body can safely disperse the lightning energy into the earth
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The power line and communication line entering the building should be installed at the junction of lpz0 and lpz1, lpz1 and lpz2, and at the front end of terminal equipment
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The AC power line leading into the power supply room shall be equipped with corresponding low-voltage arrester and equipment for protecting transverse voltage outdoors
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About the grounding specification of the computer room, in this issue, we will learn about the lightning protection and grounding related construction methods of the computer room
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The following measures should be taken to reduce the electrochemical corrosion of grounding body (including lightning protection, repeated grounding of AC zero line, protective grounding, combined grounding, cable metal sheath, and various natural grounding bodies), underground lead wire and ground bare conductor connection: ① galvanized steel, cast steel, copper or graphite electrode should be used for grounding body (including underground lead wire); ② Reduce the DC working current of the combined grounding system; ③ there should be no DC or AC current in the protective grounding system; ④ the lead-in cable should adopt the cable with insulated outer sheath or the metal outer sheath of the cable should be insulated from the indoor grounding system; ⑤ When two different metal wires (or metal bars) are connected, fusion welding shall be used as far as possible to ensure no false welding and false welding
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All kinds of grounding systems (including combined grounding, protective grounding, lightning protection grounding, and various natural grounding bodies) in communication room have two setting modes (separate setting mode and combined setting mode), but only one setting mode is allowed in each place
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The advantages and disadvantages of the design depend on the comprehensive consideration of many factors of the local soil environment
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It is divided into artificial grounding body and natural grounding body
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② Protective grounding bar and combined grounding bar shall be installed respectively in the power supply room
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The joint grounding system shall be connected to the joint grounding bar according to the classification of the mechanical room, and the connection places are as follows: ① one pole of various DC power buses to be grounded; ② lead-in rack, test rack, test land of lead-in rack, measuring platform, test bench, and grounding of test instruments; ③ metal rack of each mechanical room not connected to AC power supply (DC distribution panel rack of the power room shall not be grounded); ③ the grounding of the joint grounding system shall be connected to the joint grounding bar according to the classification of the mechanical room; ④ Working grounding of telegraph machinery and automatic telephone repeater; ⑤ insulating metal sheath of lead-in cable and metal shielding layer of distribution cable; ⑥ security lightning arrester of communication machinery room (including discharge gap, lightning arrester, etc.); ⑦ independent grounding of panel frame prone to noise interference
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There are three ways for lightning to enter the communication room: the first is direct lightning strike, which directly hits the metal wire, so that the high-voltage lightning propagates along both sides of the wire in the form of wave and is introduced into the room; the second is the high voltage pulse from the induction lightning, that is, due to the lightning cloud discharging on the ground; the third is the lightning protection construction method; The third is the electrostatic induction and electromagnetic induction formed by the rapid discharge between thunderstorm clouds
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This counterattack will be transmitted into the room in the form of waves along the zero line of the power system, protective grounding wire and various forms of grounding wire
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The equipotential connection must be made at each crossing point when the electrical channel, metal pipe and other metal components pass through all levels of lightning protection areas
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When adopting the separate grounding mode, the following measures should be taken: (1) the distance between various underground grounding bodies and underground bare leads should be more than 20m, and the grounding pile should be set at the place where the grounding device is buried
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According to iec1312 – lightning electromagnetic pulse protection standard, power SPD and communication network SPD (transient overvoltage protector) should be installed
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Grounding body: also known as grounding electrode, it is a metal conductor or conductor group in direct contact with soil
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Through the main reinforcement of the building, the upper end of the building is connected with the lightning arrester, the lower end is connected with the ground grid, and the middle is connected with the grading net or ring grading belt of each floor
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It is not allowed to use the neutral line of AC three-phase four wire system to replace the protective grounding
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The damage of lightning overvoltage to internal electronic equipment is mainly introduced along the line
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The interface of the protected area is formed by shielding layer composed of external lightning protection system, reinforced concrete and metal shell of the building
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The protective grounding system is connected to the protective grounding bar according to the equipment, and the connection places are as follows: ① AC distribution board, rectifier, other AC power equipment, and the frame and shell connected to the AC power supply; ② metal sheath of AC power line; ③ repeated grounding of neutral line of AC three-phase four wire distribution system
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The lead of grounding body shall not be protected by steel pipe, and insulation measures shall be taken
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Practice requires systematic Grounding Theory to guide the engineering practice
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SPD is an effective means to protect electronic equipment from conducting surge overvoltage caused by lightning and other interference
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The equalizing equipotential connection is implemented for all kinds of metal pipelines entering the building, and the equipotential treatment is carried out for all kinds of ground wires with special requirements
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The connecting wire from the equipment in the communication room to the reflux bar
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The factors such as soil resistivity, soil structure, water content and constructable area determine the shape, size and material selection of grounding grid
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2、 Design principle: communication line and communication machinery grounding are designed for lightning protection, strong current protection, electromagnetic induction protection, electric corrosion protection, communication interference protection, normal communication work and personal safety protection
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Grounding device is the general name of grounding body and ground wire, whose function is to lead the lightning current into the underground, and the protection of lightning protection system is related to this to a large extent
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The characteristics of the grounding project itself determine the influence of the surrounding environment on the project effect
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The copper core shall not be less than 35mm2 (from the main distribution frame to the grounding bar); the copper core shall not be less than 16mm2 (for communication equipment when the grounding resistance is required to be less than 10 Ω); the copper core shall not be less than 10mm2 (for communication equipment when the grounding resistance is required to be more than 10 Ω); the aluminum core shall not be less than 25mm2 (for power frequency AC equipment)
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According to the division requirements of lightning protection area, the external part of the building is the direct lightning strike area; the location of the internal part of the building and the computer room is the non exposed area, and the more to the internal part, the lower the risk
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