Lightning protection and grounding is an important sub-division of building electrical engineering, which is often a difficult point in construction engineering because of its strong professionalism and more concealed projects. This article explains in detail the 15 process nodes of lightning protection and grounding construction, and attaches examples of excellent engineering pictures for your reference to guide construction or inspection.
01 lightning protection down line
Process description: the welding of the grounding device should be lap welding, and the lap length should meet the following requirements: the lap between the flat bar and the flat bar is 2 times the width of the flat bar, not less than three sides of the welding; the lap between the round bar and the round bar is 6 times the diameter of the round bar, and the double-sided welding; the lap between the round bar and the flat bar is 6 times the diameter of the round bar, and the welding is applied on both sides; the flat bar and the steel pipe, the flat bar and the angle steel are welded, and the outer two sides of the angle steel are closely adhered to, or the surface of the 3/4 steel pipe is tightly welded, and the upper and lower sides are welded; in addition to the welded joints buried in the concrete, there are anti-corrosion measures.
Lightning protection down the line
02 Down lead identification
Process description: Each layer of the main reinforcement of the building column as the grounding down conductor is painted with yellow paint at 0.3m from the ground, and the length of the painting is 10cm.
Down lead identification
03 Roof lightning protection belt
Process description: the lightning cable should be laid horizontally or vertically, and can also be laid in parallel with the inclined structure of the building; the lightning cable should be straight and firm, and there should be no ups and downs and bending, and it should be 100mm away from the surface of the building. The distance between the supporting parts should be 0.5~1.5m in the horizontal straight part, 1.5~3m in the vertical part, and 0.3~0.5m in the turning part. Hot-dip galvanized steel will be damaged during welding, and anti-corrosion treatment should be done within 100mm of the welding mark. Metal nameplates should be used to make permanent identifications at lightning protection wires.
Lightning protection belt over expansion joints
The lightning belt is connected to the down conductor
The lightning strip is marked with a down lead
04 Ground resistance test point
Process description: The artificial grounding device or the grounding device using the building foundation reinforcement must be set up above the ground according to the design requirements. The test point should form a disconnect card, which is usually fastened with galvanized bolts to facilitate inspection and testing. If the junction box is canceled, the fixing parts of the hole cover should be embedded on the cave wall, and the inner wall should be wiped with cement mortar. The production of the test point should be combined with the exterior decoration of the building to be practical and beautiful.
Ground resistance test points
05 Grounding of metal pipes on the roof
Process description: The roofing metal pipe must be grounded reliably, not directly welded, and must be connected with the grounding flat steel by using the grounding snap ring and the copper core flexible wire, and the anti-loosening parts are complete.
Roofing metal pipes are grounded
06 Grounding of metal components on the roof
Process description: Other exposed metal components of the roof must be connected with the lightning protection belt to form an integral electrical path. Each component shall not be connected in series, and must be connected separately with the grounding trunk.
Metal staircase grounding
Grounding of metal components
The roof casing is grounded
07 Indoor metal doors and windows are grounded
Process description: When the height of the building exceeds 45m, the railings, doors and windows and other large metal objects on the outer wall of 45m and above should be connected to the lightning protection device directly or through embedded parts. When the height of the building exceeds 60m, the large metal objects such as railings, doors and windows on the outer wall of 60m and above should be connected to the lightning protection device directly or through embedded parts. When the metal doors and windows are grounded, the connecting conductor should be concealed, and should be carried out after the window frame is positioned and before the construction of the wall decoration layer or plastering layer.
Indoor metal doors and windows are grounded
08 The metal shell of the lamp is grounded
Process description: When the height of the lamp is less than 2.4m from the ground, the accessible bare conductor of the lamp must be grounded (PE) or zero (PEN) reliably, and there should be a special grounding bolt.
The metal housing of the luminaire is grounded
09 The distribution box is connected to the metal conduit
Process description: The metal frame and basic steel of cabinets, screens, tables, boxes and plates must be grounded (PE) or zero (PEN) reliably; The connection between the metal conduit and the distribution box must be grounded and jumped, and each pipeline must be connected with the busbar or grounding trunk line separately, and shall not be connected in series.
The distribution box is crossed with a metal conduit
10. The door (frame) of the distribution room is grounded
Process description: The grounding jumper must be used between the door and the door frame of the substation and distribution room, and be connected with the indoor grounding trunk to form a good electrical path. The grounding connection at the fence door of the distribution room isolation and static compensation device and the hinge of the metal door of the substation and distribution room shall be braided copper wire. The lightning arrester in the substation and distribution room should be connected with the grounding trunk with the shortest grounding wire.
The door (frame) of the distribution room is grounded
11 Grounding of electrical equipment
Process description: The grounding of each electrical device should be connected with the grounding busbar or grounding trunk line with a separate grounding wire, and it is strictly forbidden to connect several electrical devices that need to be grounded in series in one wire. Important equipment and equipment structures should have two grounding conductors connected to different locations of the main grounding grid. And each grounding down wire should meet the requirements of thermal stability and mechanical strength, and the connecting lead should be convenient for regular inspection and testing.
Grounding of electrical equipment
12 Jumper of metal pipes
Process description: The connection of metal pipes generally does not need to be connected with jumper wires. However, the water meter of the water supply system and the small section of plastic pipe in the metal pipe need to be added with jumper wires to ensure the effective equipotential bonding and grounding of the metal pipeline.
Metal pipe jumper
13 Grounding trunk of the distribution room
Process description: the installation requirements of the grounding trunk in the substation and distribution room: the grounding device is easy to check, and the laying position does not hinder the dismantling and maintenance of the equipment; when laying horizontally along the building wall, the height from the ground is 250~300mm; the gap between the building wall is 10~15mm; when the grounding wire crosses the deformation joint of the building, a compensation device is provided; the surface of the grounding wire is 15~100mm along the length direction, and each section is 15~100mm, which is painted with yellow and green stripes respectively; No less than 2 binding posts or grounding bolts for temporary grounding should be set on the grounding trunk of the high-voltage distribution room. A rat guard must be set at the door of the substation and distribution room, and the height of the rat guard shall not be less than 60cm.
Grounding trunk of the distribution room
Grounding trunk of the distribution room
Switchroom rat guards
14 Total equipotential bonding
Process description: The building equipotential connection trunk should be drawn from the grounding trunk or the total equipotential box that has no less than 2 direct connections with the grounding device, and the connecting line between the equipotential connection trunk line or the local equipotential box forms a ring network, and the ring network should be connected with the equipotential bonding trunk or local equipotential box nearby. Branches should not be connected in series.
Total equipotential bonding
15 Local equipotential bonding
Process Description: Equipotential coupling terminal plates should be bolted so that they can be disassembled for regular testing. After the installation of equipotential bonding, the continuity test should be carried out, and the power supply for the test can use DC or AC power supply with a no-load voltage of 4~24V, and the test current should not be less than 0.2A. Equipotential bonding is considered effective when the resistance between the equipotential bonding terminal board and the ends of a metal body, such as a metal pipe, within the range of equipotential bonding, does not exceed 3 Ω. If a pipe connection with poor conduction is found, it should be used as a jumper wire, and conductivity tests should be carried out regularly after it is put into use.
Local equipotential bonding
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