GB 50689-2011Code for design of lightning protection and earthing engineering for telecommunication bureaus (stations) (English PDF)

2.0.1 Lightning protection zones (LPZ)

An area that is prone to lightning strikes is divided into protected areas according to the different environments of the communication bureau (station) building, communication room, and protected equipment. The protected area is called a lightning protection area.

2.0.2 Thunderstorm day

A day in which more than one thunderstorm is heard is called a thunderstorm day.

2.0.3 Low keraunic zones

A less-mined area refers to an area where the annual average number of thunderstorm days does not exceed 25.

2.0.4 Middle keraunic zones

The middle minefield refers to the area where the annual average number of thunderstorm days is within 26-40.

2.0.5 High keraunic zones

A minefield is an area with an average number of thunderstorm days within 41 to 90 a year.

2.0.6 Strong keraunic zones

A strong minefield is an area with an average number of thunderstorm days exceeding 90 a year.

2.0.7 Keraunic zones

According to the number of annual average thunderstorm days, it is divided into few minefields, medium minefields, many minefields and strong minefields.

2.0.8 Evaluation of lightning strike risk

According to various factors of lightning strikes, it is a method to comprehensively evaluate the degree of damage to the station (station) caused by lightning strikes to determine the protection level and category.

2.0.9 Direct lightning flash

Lightning that strikes directly on a building or lightning protection device.

2.0.10 Direct stroke protection

Measures to prevent lightning from directly striking buildings, structures, electrical networks or electrical installations.

2.0.11 Air-terminal system

Lightning rods, lightning belts (wires), and lightning nets that directly accept lightning strikes.

2.0.12 Rolling sphere method

A simplified analysis method for the application of electrical geometry theory in the lightning protection analysis of buildings.

2.0.13 Down-conductor system

The metal conductor connecting the air-termination device to the grounding device.

2.0.14 Lightning electromagnetic pulse (LEMP)

Electromagnetic radiation associated with lightning discharges. The resulting electric and magnetic fields can couple into electrical or electronic systems, creating damaging surge currents or voltage surges.

2.0.15 External lightning protection system

It is composed of lightning receptors, down conductors and grounding devices, and is mainly used as a protective device against direct lightning strikes.

2.0.16 Soil resistivity earth resistivity

A parameter that characterizes the electrical conductivity of the soil. Its value is equal to the resistance measured between the opposite sides of the soil per unit cube, and the unit is ohm·m.

2.0.17 Power frequency ground resistance power frequency ground resistance

When the power frequency current flows through the grounding device, the resistance between the grounding body and the remote earth. Its value is equal to the ratio of the voltage of the grounding device relative to the remote earth to the current flowing into the ground through the grounding body.

2.0.18 Common earthing

Different grounding methods of various communication equipment in communication bureaus (stations), including working grounding, protective grounding, shielding grounding, anti-static grounding, information equipment logic grounding, etc. The protective grounding of the lightning arrester is connected together, and the grounding method of the basic grounding body of the building and the peripheral grounding system is used together with the lightning protection grounding of the building.

2.0.19 Earth electrode

A conductor or a group of conductors that are in close contact with the soil (earth) and provide an electrical connection to the soil (earth) for the purpose of connection to the earth.

2.0.20 Earthing lead-in wire earth connection

The connecting line between the grounding body and the general grounding busbar is called the grounding lead-in line.

2.0.21 Earthing system earthing system

All electrical connections and devices included in the grounding of systems, devices and equipment, including grounding bodies buried in the ground, grounding wires, cable shields connected to grounding bodies, and equipment shells or exposed metal parts connected to grounding bodies, building A complex system including material reinforcement and frame.

2.0.22 Earth grid

A group of grounding bodies composed of interconnected bare conductors buried in the ground to provide a common ground for electrical equipment or metal structures.

2.0.23 Earth-termination system

The sum of ground wire and ground body.

2.0.24 Equipotential bonding equipotential bonding

Connect separate devices and conductive objects with equipotential bonding conductors or lightning arresters to reduce the potential difference between them caused by lightning current.

2.0.25 Equipotential bonding network bonding network

A network of conductors equipotentially bonding exposed conductive parts of a system.

2.0.26 Earthing reference point (ERP)

The only point of connection between the common earthing system and the system's equipotential bonding network.

2.0.27 Grounding collection line mail earth conductor

Refers to the strip-shaped copper bar or flat steel used as a grounding conductor. It is usually used as the main line of the grounding system in a communication bureau (station). Strip ground pooling wire.

2.0.28 Earth terminal

Connection terminal or grounding bar for the grounding wire.

2.0.29 Earthing bar

It is a rectangular copper bar connected to the ground bus bar and used as a connection terminal for various ground wires.

2.0.30 Main earthing terminal (MET)

The grounding bar used to connect various grounding wires to the grounding device is the first-level grounding bar of the system.

2.0.31 Floor equipotential earth terminal board (FEB)

In the building, the grounding bar set on the floor is used for local equipotential grounding bar for equipotential connection.

2.0.32 Local grounding row 1ocal equipotential earthing terminal board (LEB)

In the equipment room of the communication system, make a ground bar for local equipotential connection.

2.0.33 Cable entrance earthing bar (CEEB)

The grounding bar that can connect each outdoor cable of the cable entry facility with the general grounding bar or the ring grounding body through the grounding bar.

2.0.34 Cable entrance facility cable entrance facility (CEF)

Connect the grounding inside the cable and the metal sheath to the grounding facility as close as possible to the entrance of the outdoor cable according to the actual situation.

2.0.35 Common DC return (DC-C)

A DC power supply system in which the DC return conductor is connected to the surrounding network at multiple points.

2.0.36 Isolated DC return (DC-I)

A DC power supply system in which the DC return conductor is connected to the BN at a single point.

2.0.37 Common bonding network (CBN)

The main means of connection and grounding in the communication bureau (station), it is a group of metal parts that are deliberately interconnected or accidentally interconnected to form the main connection network of the building.

2.0.38 Vertical trunk grounding wire vertical reise(VR)

A group of vertical conductors that provide an engineering low-resistance path between telecommunication equipment and the main grounding terminal, and vertically run through the main line for grounding on each floor of the communication bureau (station) building.

2.0.39 Lightning over-voltage lightning over-voltage

Transient overvoltage at a system port due to lightning discharge.

2.0.40 Surge protective devices (SPD)

It is used in communication bureaus (stations) as a device for protecting lightning overvoltage and operating overvoltage in various communication systems.

2.0.41 Voltage limiting type SPD

Voltage-limiting SPDs are generally composed of components such as metal oxide varistors or semiconductor protection devices, and communication bureaus (stations) must use voltage-limiting SPDs.

2.0.42 Maximum continuous operating voltage

The maximum AC voltage rms or DC voltage that is allowed to be permanently applied to the SPD. Its value is equal to the rated voltage.

2.0.43 Residual voltage

When the discharge current flows through the SPD, the peak voltage between its terminals.

2.0.44 Limit voltage residual voltage of SPD

The maximum peak voltage measured between SPD terminals when an impulse voltage of specified waveform and amplitude is applied.

2.0.45 Nominal turn-on voltage nominal start-up voltage

The starting voltage of metal oxide varistors under the condition of applying a constant 1mA DC current.

2.0.46 Nominal discharge current (In)

The index indicating the flow capacity of SPD corresponds to the impulse current of 8/20µs simulated lightning wave.

2.0.47 Maximum discharge current(Imax)

The SPD will not be substantially damaged, and each line (or single module) can simulate the maximum current peak value of the lightning wave through the specified number of times and the specified waveform. The maximum flow capacity is 2.5 times of the nominal discharge current.

2.0.48 Two-port SPD

SPD with independent input and output ports. A dedicated series impedance is inserted between these ports.

2.0.49 One-port SPD

The SPD is connected in parallel with the circuit to be protected. A port can separate the input and output terminals, there is no special series impedance between the input and output terminals.

2.0.50 Global positioning system (GPS)

A technology that combines satellite and communication development, using navigation satellites for time measurement and distance measurement.

3.1 General provisions

3.1.1 The grounding system of the communication bureau (station) must adopt the joint grounding method.

3.1.2 Large and medium-sized communication bureaus (stations) must use TN-S or TN-CS power supply.

3.1.3 Small communication bureaus (stations), mobile communication base stations and small sites can use TT power supply.

3.1.4 All kinds of wireless stations installed on civil buildings should ensure the safety of the power supply system in the buildings.

3.1.5 The design of lightning overvoltage protection shall comply with the relevant provisions of Chapter 9 of this code, and the installation of lightning arresters shall comply with the relevant provisions of Appendix C of this code.

3.2 Composition of grounding system

3.2.1 The grounding system of communication bureau (station) can be designed according to Figure 3.2.1.

3.2.2 Grounding collection lines and grounding lines should be connected in a layer-by-layer radiation manner, preferably in a layer-by-layer dendrite or mesh connection, and should meet the following requirements.

1 The vertical grounding collection line should run through each floor of the communication bureau (station) building, one end of which should be connected with the grounding lead-in line, and the other end should be connected with the steel bars of each layer of the building body and the horizontal grounding collection line of each floor, and should form radiation shape structure. The vertical grounding collection line should be connected to the ring grounding collection line at the bottom of the building (structure), and should be vertically led to the horizontal branching grounding collection line of each machine room.

2.The horizontal grounding and pooling lines should be arranged in layers, and the grounding lines of each communication equipment should be introduced from the horizontal grounding pooling line of the layer nearby.

3.2.3 The combined ground network of the communication bureau (station) should use the steel bars in the building foundation concrete and the ring grounding body laid around the building, as well as the cable shielding layer and various pipelines connected to it to maintain electrical connection with each other.

3.3 Ground body

3.3.1 The upper end of the grounding body should not be less than 0.7m from the ground. In cold regions, the grounding body should be buried below the frozen soil layer. In rocky mountains with thin soil or gravel and rocky areas, the grounding body burial depth should be determined according to specific conditions.

3.3.2 The vertical grounding body should use hot-dip galvanized steel, copper, copper-clad steel and other grounding bodies with a length of not less than 2.5m, and it can also be determined according to the soil quality and geographical conditions of the buried ground network. The distance between vertical grounding bodies should not be less than 5m, and the specific number can be determined according to the size of the ground grid and the geographical environment. Vertical grounding bodies should be buried at the joints of the four corners of the ground grid.

3.3.3 In areas with high soil resistivity, when the grounding resistance value of the local network is difficult to meet the requirements, the radial grounding body can be extended outward, and the liquid long-term resistance reducing agent, grounding rod and external grounding can also be used..

3.3.4 When the urban environment does not allow the conventional grounding method, the grounding rod grounding method can be used.

3.3.5 The horizontal grounding body should be made of hot-dip galvanized flat steel or copper. The horizontal grounding body should be welded to the vertical grounding body.

3.3.6 When the grounding body is made of hot-dip galvanized steel, its specifications should meet the following requirements.

1 The wall thickness of the steel pipe shall not be less than 3.5mm.

2 The angle steel should not be smaller than 50mm×50mm×5mm.

3 The flat steel should not be smaller than 40mm×4mm.

4 The diameter of round steel should not be less than 10mm.

3.3.7 When the grounding body is made of copper-clad steel, copper-plated steel rod and copper-plated round steel, its diameter should not be less than 10mm. The coating thickness of copper-plated steel rods and copper-plated round steel shall not be less than 0.254mm.

3.3.8 Except for all welding points between grounding bodies in concrete, all welding points between other grounding bodies should be treated with anti-corrosion treatment.

3.3.9 The welding length of the grounding device shall not be less than 2 times of its width when flat steel is used, and shall not be less than 10 times of its diameter when round steel is used.

3.4 Ground lead-in

3.4.1 The grounding lead-in wire should be treated with anti-corrosion treatment.

3.6.7 The connection points at both ends of the ground wire should ensure good electrical contact.

3.6.8 It is strictly forbidden to install switches or fuses in the grounding wire.

3.6.9 The grounding wire drawn out from the grounding pooling line should be clearly marked.

3.7 Equipotential bonding method

3.7.1 Mesh (M), star (S) and star-mesh hybrid equipotential connections for communication systems can be designed according to Figure 3.7.1.

3.7.2 The communication system should choose the equipotential connection method according to the distribution of communication equipment and the area of the computer room, the immunity of communication equipment and the grounding method inside the equipment.

3.8 Incoming methods of various cables

3.8.1 All kinds of cables should be buried underground.

3.8.2 Cables without metal outer sheath should be introduced through steel pipes, and both ends of the steel pipes should be grounded.

3.8.3 For the transmission optical (electrical) cables entering and leaving the communication office (station), all kinds of cables should be concentrated in the incoming line room, and the metal armored outer sheath should be directly grounded with a special grounding card in the incoming line room, the metal components in the cable should be grounded at the terminal, the metal sheaths and metal components of various cables should be grounded at both ends, and the metal outer sheaths of various signal lines and cables should be grounded in the incoming room. Or connect to the ground grid.

3.8.4 The grounding points of various types of cable metal sheaths and metal components should avoid being set up or introduced near the pillars used as lightning downconductors.

3.9 Ground wire laying requirements

3.9.1 When the grounding wire is connected to the equipment and the grounding bar, a copper terminal must be added, and it should be pressed (welded) firmly.

3.9.2 The size of the terminal should match the diameter of the grounding wire. The contact part of terminal block, equipment and grounding bar should be flat, fastened, and free from rust and oxidation.

3.9.3 The grounding wire shall adopt a flame-retardant cable whose outer sheath is marked with yellow and green alternate colors, and may also use plastic insulation with a yellow and green logo on the end where the grounding wire is connected to the equipment and the grounding bar. bring.

3.10 Protection of computer network interface and control terminal interface

3.10 Protection of computer network interface and control terminal interface

3.10.1 Computer network interface, control terminal Ethernet port, RS232, RS422, RS485 and other interfaces and cables shall be equipped with SPD according to the relevant provisions of Chapter 9 of this specification.

3.10.2 The SPDs of computer interfaces, control terminals, and network data lines shall meet the transmission rate requirements of various interface devices, and the line positions, line rows, and line sequences of SPD interfaces shall be compatible with the protected equipment interfaces.

3.10.3 The computer control center or control unit must be set in the middle of the building, and must avoid the lightning current distribution channel where the lightning surge is concentrated, and the computer is strictly prohibited from directly using the power socket on the outer wall of the building.

3.11 Grounding and Interface Protection of Centralized Monitoring System

3.11.1 In the middle minefield and above the lightning active area, anti-wave...