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General regulations 1
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Outdoor distribution lines should be laid with cables
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It is not suitable to use single insulated wire overhead laying
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2
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The distribution box and switch box shall adopt the standardized products produced by professional manufacturers, and shall meet the requirements of low voltage switchgear and control equipment Part 4: special requirements for complete sets of equipment (ACS) for construction site (gb7251.4), technical code for safety of temporary electricity on construction site (jgj46) and standard for safety inspection of building construction (jgj59), and shall be recognized by “3C” The electrical components such as disconnector, leakage protector and insulated conductor used in the distribution box must also obtain the “3C” certification
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3
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When there are more than 5 sets of temporary power equipment or the total capacity of the equipment is 50KW or above, the construction organization design of temporary power shall be prepared
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The construction organization design of temporary power utilization shall be organized and compiled by the electrical engineering technicians, and can be implemented only after being approved by the technical director of the enterprise and the chief supervision engineer of the project
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When the design of temporary power construction organization is changed, it shall be approved according to the original procedure
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4
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Safety technical files must be established for temporary power use on construction site
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The safety technical files shall include the following contents: 1) all data of power consumption organization design; 2) data of modification of power consumption organization design; 3) data of power consumption technical disclosure; 4) check and acceptance table of power consumption engineering; 5) test and inspection voucher and commissioning record of electrical equipment; 6) record table of determination of grounding resistance, insulation resistance and leakage action parameters of leakage protector; 7) regular check (re check) table (8) record of electrician installation, inspection, maintenance and removal
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5
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The temporary power engineering shall be inspected regularly according to the divisional and sub divisional works
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During the inspection, the grounding resistance and insulation resistance shall be rechecked
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The hidden danger found must be dealt with in time, and the check and acceptance procedures shall be performed
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Regular inspection record sheet leakage protector tester grounding resistance tester 2
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External power protection 1
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Construction in progress shall not be carried out directly under the external power overhead line, set up operation shed, build living facilities or pile up components, fixtures, materials and other sundries
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2
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Safe operation distance must be kept between the outside edge of the construction in progress (including scaffolding) and the external power overhead line
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The minimum safe operation distance shall comply with the following table: 3
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When the motor vehicle lane at the construction site crosses with the external overhead line, the minimum vertical distance between the lowest point of the overhead line and the road surface shall comply with the following table: 4
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It is strictly forbidden for the crane to cross the external overhead line without protective facilities
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When hoisting near the external overhead line, the minimum safe distance between any part of the crane or the edge of the object to be hoisted at the maximum deflection and the side line of the overhead line shall meet the following table: 5
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When the above safety distance cannot be met, the external power line protection scheme must be prepared, insulation isolation protection measures must be taken, and eye-catching warning signs shall be hung
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When erecting protective facilities, it must be approved by relevant departments, and temporary power cut or other reliable safety technical measures shall be adopted, and it shall be supervised by electrical engineering technicians and full-time safety personnel
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6
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The protective facilities shall be firm and stable, the protective barrier shall be set up with insulating materials, and the isolation protection of external power lines shall reach IP30 level (to prevent 2.5mm solid intrusion)
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External power protection measures 7
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When the minimum safety distance between the protection facilities and the external power lines does not meet the requirements in the table below, it is necessary to negotiate with the relevant departments to take measures such as power cut, relocation of external power lines or change of project location
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Construction without the above measures is strictly prohibited
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8
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It is strictly forbidden to set up the upper and lower ramps of scaffolds on the side with external power lines
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9
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The erection of temporary facilities on site and the installation position of building lifting machinery should avoid the side with external power lines
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3
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Grounding and neutral protection system 1
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In TN-S neutral protection system supplied by special transformer at construction site, the metal shell of electrical equipment must be connected with special zero line
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The protection zero line shall be led out from the working ground wire, the zero line at the power supply side of the distribution room (main distribution box) or the zero line at the power supply side of the main leakage protector
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2
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When the construction site and external power lines share the same power supply system, the grounding and neutral protection of electrical equipment shall be consistent with the existing system
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It is not allowed to connect one part of equipment to neutral and the other part to ground
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When TN system is used as protective neutral connection, the working zero line (N line) must pass through the total leakage protector, and the protective zero line (PE line) must be led out from the repeated grounding of the zero line of the power incoming line or the zero line of the power side of the total leakage protector to form a local TN-S neutral connection protection system
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When the power incoming line is three-phase and five wire, the wiring in the general distribution box (when the box type transformer is connected) and the power incoming line is three-phase and four wire, the wiring in the general distribution box (when the transformer is connected) 3
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The grounding wire of each grounding device shall use two or more conductors to make electrical connection with the grounding body at different points
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Aluminum conductor shall not be used as grounding body or underground grounding wire
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Angle steel, steel pipe or smooth round steel shall be used for vertical grounding body, and threaded steel shall not be used
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The natural grounding body can be used for grounding, and it is better to connect with the foundation grounding grid of the project under construction, so as to ensure its electrical connection and thermal stability
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Repetitive grounding device 1 (NATURAL grounding body adopted) repetitive grounding device 2 (artificial grounding body adopted) 4
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The protective zero line in TN system must be repeatedly grounded not only in the distribution room or main distribution box, but also in the middle and end of the distribution system
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In TN system, the grounding resistance of each repeated grounding device of protective zero line should not be greater than 10 Ω
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In the power system where the working grounding resistance is allowed to reach 10 Ω, the equivalent resistance of all repeated grounding shall not be greater than 10 Ω
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5
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It is forbidden to install switch or fuse on PE line
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It is strictly forbidden to mix PE line with N line, and PE line is strictly forbidden to break
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6
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When the material of PE line is the same as that of phase line and working zero line (N line), the minimum section of PE line shall meet the requirements in the table below
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The insulation color of PE wire is green / yellow
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7
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The metal box of the distribution box, the metal shell and bracket of the construction machinery, lighting appliances and electrical devices and other non electrified exposed conductive parts shall be protected and connected to the neutral line, and the copper nose connection shall be adopted
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The door of construction machinery protection neutral connection distribution box is used for protection neutral connection, overhead cable suspension cable and support, overhead line support is used for connection node of protection neutral connection, protection neutral connection adopts stranding connection mode (error) 4 4
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Distribution box, switch box 1, distribution system should be set with distribution cabinet or main distribution box, distribution box and switch box, three-level distribution should be implemented, and all levels of distribution boxes should be connected with each other Leakage protectors shall be installed for all equipment
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The setting of distribution box and switch box shall meet the following requirements: (1) several distribution boxes can be set below the main distribution box; (2) the three-level protection diagram of three-level distribution; (3) the main distribution box shall be set in the area close to the power supply, and the distribution box shall be set in the area with relatively concentrated electric equipment or load; (3) the distance between the distribution box and the switch box shall not exceed 30m, The horizontal distance between the switch box and the fixed electrical equipment controlled by it should not be more than 3m; the distance between the distribution box, switch box and mechanical equipment should be centralized (wrong) the switch box should have enough space and passage for two people to work at the same time around the distribution box and switch box, and there should not be any objects that hinder the operation and maintenance, shrubs and weeds
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There is enough operation space in front of the distribution box (there is protection around) there are sundries stacked in front of the distribution box (error) 2
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Power distribution box and lighting distribution box, power switch box and lighting switch box should be set separately
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3
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Each electrical equipment must have its own special switch box
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It is strictly forbidden to use the same switch box to directly control two or more electrical equipment.
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