1. In the vicinity of the machine room around the dugout as a ring for a new ground network, and from the artificial grounding network lead to the grounding trunk into the grounding bus in the machine room.
2. Artificial grounding network of vertical grounding body using 10 40 * 4mm * 2000mm galvanized steel angle and 10 grounding module, horizontal grounding using 50mm × 5mm galvanized flat steel connected.
3. Galvanized angle steel or grounding module should be used for vertical burial, the depth of which is 2m, and the top of which should be 0.6m below the soil layer (or permafrost layer) after burial, and the distance between each vertical grounding body is 5m, with a minimum of 4m.
4. Vertical grounding bodies must be welded to each other or to the ground wire, and welding slag must be removed from the welded area and anticorrosive paint must be applied.
5. Horizontal grounding body interconnection and lap connection with vertical grounding body using welding. Flat steel and flat steel grounding wire lap length of 2 times the width, not less than 3 sides of the welding. Round steel grounding wire lap length is 6 times the diameter of round steel, and should be 2-sided welding. Round steel and flat steel lap for 6 times the diameter of round steel, and should be 2-sided welding. Flat steel and steel pipe, flat steel and angle welding, close to the outside of the angle on both sides or close to the surface of 3/4 steel pipe, up and down welding.
6. Reducing agent and water according to the ratio of 1 : 1 in the container and mix well; will be mixed with a good lowering agent laid around the vertical grounding body, lowering agent laying 16-24 hours to seal the soil tamping; will be modulated to lay a layer of lowering agent along the level of the grounding body, after the completion of the soil to take a relatively fine layer of soil laid on top of the layer, thick, about 20cm, paved, spread once again after water, and finally the original soil backfill and compacting. Finally, the original soil backfill tamping. (Note: the use of resistance-reducing agent can play a role in improving the reduction of soil resistivity and isolation of grounding materials and soil direct contact, thereby reducing the speed of corrosion and oxidation of grounding materials.)
7. Backfill soil should be appropriate amount of water, layered tamping (module of the upper and lower left and right must be in close contact with the soil, and to avoid the module around the mixing of stones, sticks and other non-conductive objects), to be fully absorbed by the module moisture (24 hours) after the measurement of grounding resistance.
8. Exposed grounding wire can be introduced into the machine room through galvanized steel pipe.
9. The resistance value of the ground network is required ≤ 1Ω.
10. The distance between the ground network and the pedestrian walkway should be maintained at a distance of more than 3m to ensure the personal safety of pedestrians. Difficulties in the actual construction, it is necessary to pass through the pedestrian passage at the grounding flat steel should be wrapped in asphalt or linoleum, the necessary anti-step voltage treatment.
Attachment I: the grounding system schematic diagram is as follows:
(2) machine room voltage equalization and equipotential part
Equipotential connection is the building, nearby all the metal objects are connected with electrical methods, so that the whole building becomes a good equipotential body. When lightning strikes the building, inside and near the building is basically an equipotential body, so there will be no internal equipment and people are struck by lightning or high potential counterattack. Equipment in the equipment room isoelectric grounding methods are as follows:
Machine room with 30 * 3 copper rows were laid along the machine room around the same time with copper foil 600mm * 600mm tic-tac-toe grid along the electrostatic floor keel paving, the formation of the machine room equal voltage equipotential network. In each computer room set up 1 equipotential box, the artificial grounding network and computer room equalization equipotential network connected together.
The equipment shells in the server room are grounded for lightning protection, and the switch shells, racks, server metal shells, and UPS battery cabinet shells in the server room are grounded nearby.
Anti-static floor keel in the computer room shall be connected with a grid of grounding wire ("well" grid), and then connected to the equipotential bus in the computer room.
Metal pipes, roof metal keel, metal doors and windows and other metal objects in the server room are connected to the equipotential bus in the server room.
Connect the grounding of the lightning arrester and the AC ground of the equipment to the equalizing equipotential ring.
The equipment in the computer room working ground, protective ground, lightning ground, anti-static grounding and other grounding wires are connected to the equalized equipotential network. The grounding line should be as short as possible, straight. Through this way to make the equipment in the machine room to form an equipotential network, to avoid causing potential backlash and interference. All metal conductor shells in the room are 6mm2 copper wire to the shortest distance to connect to the machine room equalizing equipotential network, so that all the equipment in the room is in an equipotential state.
Attachment II: Equalization of voltage equipotential grounding schematic
(C) power lightning protection part:
According to the IEC proposed DBSG technology and lightning protection area and the division of local thunderstorms and lightning storms intensity, lightning grounding system induced lightning overvoltage protection can be shunted according to the multilevel to protect. General power supply lightning protection using three-level protection, through the power supply B, C, D three-level power supply level by level discharge of lightning current to achieve the requirements of the protection of equipment. General B level with a larger flux of lightning protection, can be larger lightning current leakage into the ground, to achieve the purpose of limiting the current, while reducing the overvoltage to a certain extent; C, D level lightning protection with a lower flux of lightning protection, can be the line in the amount of the remaining lightning leakage into the ground to achieve the effect of limiting the overvoltage to the level of the equipment can withstand.
When a lightning strike occurs when the electromagnetic intensity is relatively strong, power and communication cables are very susceptible to induced lightning attacks, induced overvoltage along the communication and power lines into the equipment, thereby damaging the equipment, therefore, the room total power distribution into the installation of the first level of power protection (B level) to ensure the safety of the entire room equipment, and 80% of the overvoltage leakage into the earth to play the role of primary protection. The role of primary protection, due to the overvoltage of the power supply line has been the first discharge, but in the back end of the line is still part of the overvoltage and B-level power lightning protection of the residual voltage added to the line, so it must also be C, D-level power protection, so that overvoltage suppression to the back end of the level of power equipment can be tolerated. For this project, the power supply three-level protection were selected B, C, D power lightning protector each group, respectively, they are installed in the computer room at the input of the main distribution cabinet, UPS power input, terminal equipment into the end of the line.
According to site conditions, the total distribution room is now using B + C lightning protection module, and access to the UPS input, in the front of the equipment can be through the D-level PDU lightning protection socket on the load equipment for lightning protection.
The main technical parameters of the power supply lightning protection module:
①Model: 60/4 (Class B)
Maximum continuous operating voltage: 420V
Nominal discharge current (8/20μs): 20KV
Maximum throughput capacity (8/20μs): 40KVA
Keeping level: ≤2.0kv
Response time: ≤ 25ns
Wiring wire diameter: ground wire ≥ 25mm square
Operating environment: -40℃ - +80℃
Shell protection level: IP20
Mounting: 35mm rail
②Model number: 40/4 (CD class)
Maximum continuous Operating Voltage: 420V
Nominal Discharge Current (8/20μs): 30KVA
Maximum Throughput Capacity (8/20μs): 60KVA
Holding Level: ≤2.2kv
Response Time: ≤25ns
Wiring Diameter: Ground Wire ≥25mm sq.
Working Environment: -40℃ - +80℃
Shell protection level: IP20
Installation: 35mm rail
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