grounding and zero connection protection system 1.
The protective zero line (PE line) must be led out from the repeated grounding of the power incoming zero line or the zero line on the power side of the general leakage protector to form a local TN-S zero connection protection system.
2.
When erecting protective facilities, relevant departments must be approved With the approval of the door, the temporary power failure of the line or other reliable safety technical measures shall be adopted, and the supervision of electrical engineering technicians and full-time safety personnel shall be provided.
In the TN-S zero connection protection system powered by special transformer on the construction site, the metal shell of electrical equipment must be connected with the special protection zero line.
Leakage protectors shall be installed in distribution boxes at all levels.
8.
The connection of protective zero line adopts twisted connection (error) 4、 Distribution box, switch box 1.
Outdoor distribution lines shall be laid with cables.
Natural grounding body can be used for grounding, which shall be connected with the foundation grounding grid of the project under construction, and its reliability shall be guaranteed Electrical connection and thermal stability.
The insulation color of PE line is green / yellow.
5.
When TN system is used for protective zero connection, the working zero line (N line) shall be used It must pass through the general leakage protector.
When the motor vehicle lane on the construction site crosses the external overhead line, the minimum vertical distance between the lowest point of the overhead line and the road surface shall comply with the provisions in the following table: 4.
It is prohibited to operate on the external overhead line When hoisting near the overhead line, the minimum safety distance between any part of the crane or the edge of the lifted object and the overhead line shall meet the following table: 5.
3.
2.
The protective neutral connection of construction machinery shall be made.
In addition to repeated grounding at the distribution room or main distribution box, the protective zero line in TN system must also be repeatedly grounded at the middle and end of the distribution system.
When there are 5 or more temporary electric equipment on the construction site or the total capacity of the equipment is 50KW or above, the temporary electric construction organization design shall be prepared.
The safety technical archives shall include the following contents: ⑴ all data of power use organization design; ⑵ data of modifying power use organization design; ⑶ technical disclosure data of power use; ⑷ inspection and acceptance form of power use engineering; ⑤ test and inspection vouchers and commissioning records of electrical equipment; and ⑥ grounding resistance, insulation resistance and leakage Measurement record of leakage action parameters of protector; ⑺ regular inspection (re inspection) Check the table; 8.
The setting of distribution box and switch box shall meet the following requirements: ⑴ Several distribution boxes can be set below the main distribution box; several switch boxes can be set below the distribution box; schematic diagram of three-level distribution and three-level protection; (2) the main distribution box should be set in the area close to the power supply, and the distribution box should be set in the area with relatively concentrated electrical equipment or load; (3) the distance between the distribution box and the switch box shall not exceed 30m, and the horizontal distance between the switch box and the fixed electrical equipment controlled by it It should not be more than 3m; the distance between the distribution box, switch box and mechanical equipment and the switch box should be centralized (wrong) ⑷ there should be enough space and passage for two people to work at the same time around the distribution box and switch box, and there should be no articles hindering operation and maintenance, shrubs and weeds.
6.
Fixing Socket Cross Hole Nail Plate
The crane is strictly prohibited to cross the external overhead line without protective facilities.
Repeated grounding device 1 (using natural grounding body) repeated grounding device 2 (using artificial grounding body) 4.
Temporary power works shall be inspected regularly according to divisional and subdivisional works.
The record table shall be checked regularly Leakage protector tester grounding resistance tester II.
The door of distribution box shall be protected to neutral frame Hanging steel cable and support of air cable and overhead line support shall be used as the connection node of protective zero line.
In the power system where the working grounding resistance is allowed to reach 10 Ω, the equivalent resistance value of all repeated grounding shall not be large At 10 Ω.
5.
The non electrified exposed conductive parts such as the metal box of distribution box, the metal shell and support of construction machinery, lighting appliances and electrical devices shall be protected to neutral, and the connection with the protective neutral line shall be connected with copper nose.
Overhead laying of single insulated conductor shall not be adopted.
When the temporary electric construction organization design is changed, it shall be carried out according to the original process Procedure approval.
Construction is strictly prohibited if the above measures are not taken.
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 the intrusion of 2.5mm solid) External power protection measures 7.
When the minimum safe distance between protective facilities and external power lines cannot meet the provisions in the table below, it is necessary to negotiate with relevant departments and take measures such as power outage, relocation of external power lines or change of project location.
The temporary electric construction organization design shall be prepared by the electrical engineering technicians and implemented after being approved by the technical director of the enterprise and the chief supervision engineer of the project.
2.
External power protection 1.
6.
9.
Each electric equipment must have its own special switch box.
The distribution system shall be equipped with distribution cabinet or main distribution box, distribution box and switch box to implement three-level distribution.
Erection of temporary facilities on site The installation position of building hoisting machinery shall avoid the side with external power lines.
It is strictly prohibited to use the same switch box to directly control 2 or more electric equipment..
7.
When the power incoming line is three-phase and five wire, it is connected in the general distribution box (when the box transformer is connected) when the power incoming line is three-phase and four wire, it is connected in the general distribution box (when the transformer is connected) 3.
4.
There should be enough operation space in front of the distribution box (protected around) and sundries in front of the distribution box (wrong) 2.
III.
When the construction site shares the same power supply system with the external power line, the grounding and zero connection protection of electrical equipment shall be consistent with the existing system.
The distribution box and switch box shall be finalized products produced by professional manufacturers, and shall meet the requirements of low voltage switchgear and control equipment – Part 4: special requirements for complete equipment (ACS) on 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 obtain “3C” The electrical components such as disconnectors, leakage protectors and insulated conductors used in the distribution box must also obtain “3C” certification certificate Certification.
During inspection, the grounding resistance value and insulation resistance value shall be rechecked.
Construction in progress shall not construct, erect operation shed, build living facilities or stack components, racks, materials and other sundries directly under the external power overhead line.
The grounding wire of each grounding device shall be two or more conductors, which shall be electrically connected with the grounding body at different points.
The protection zero line shall be connected by working grounding wire and distribution room (main distribution box) The zero line at the power side or the zero line at the power side of the main leakage protector is led out.
The potential safety hazards found must be handled in time, and the re inspection and acceptance procedures shall be performed.
It is strictly prohibited to mix PE line with N line, and PE line is strictly prohibited to break.
Construction in progress (including scaffolding) A safe operation distance must be maintained between the outer edge of the overhead line and the external overhead line.
It is strictly prohibited to install switches or fuses on PE line.
It is not allowed to connect some equipment to zero for protection and the other equipment to ground for protection.
Electrician installation, patrol inspection, maintenance and demolition records.
Power distribution box and lighting distribution box, power switch box and lighting switch box shall be set separately.
Angle steel, steel pipe or smooth round steel shall be used as the vertical grounding body, and threaded steel shall not be used.
When the requirements of the above safety distance are not met, the external power line protection scheme must be prepared, insulation and isolation protection measures must be taken, and eye-catching warning signs shall be hung.
Aluminum conductor shall not be used as the grounding body or underground grounding wire.
1、 General provisions 1.
Safety technical archives must be established for temporary power use on the construction site.
In TN system, the grounding resistance value of each repeated grounding device of the protective zero line shall not be greater than 10 Ω.
The upper and lower ramps of scaffold are strictly prohibited to be erected on the side with external power lines.
The minimum safe operation distance shall comply with the provisions in the following table: 3.
3.
The material of PE line is the same as that of phase line and working zero line (N line) If the same, the minimum cross-section shall comply with the provisions in the following table.
