Assembling switchgear, measuring instruments, protective appliances, and auxiliary equipment into enclosed or semi enclosed boxes or screens forms a distribution box. What are the safety technical requirements for a distribution box? Below, the technical personnel of the distribution box manufacturer have compiled 10 precautions to share with everyone:

1. All distribution box doors should be equipped with locks, and other temporary electrical equipment should not be hung or inserted inside the distribution box and switch box. It is strictly prohibited to place debris inside the switch box.

2. Each electrical device should have its own dedicated switch box. Each electrical equipment on the construction site should have its own dedicated switch box, and must meet the requirements of "one machine, one switch, one leakage". It is strictly prohibited to use the same switch appliance to directly control two or more electrical equipment (including sockets). A leakage protector must be installed in the switch box, with a rated leakage current of no more than 30ma and a leakage action time of no more than 0.1s.

3. The electrical box and switch box should be installed upright, firmly, and not upside down or skewed. The bottom of fixed distribution boxes and switch boxes should be perpendicular to the ground, with a specific distance of more than 1.3m and less than or equal to 1.5m; The distance between the bottom of mobile distribution boxes and switch boxes and the ground should be greater than or equal to 0.6m and less than or equal to 1.5m.

4. The power cord entering the high-voltage distribution box must not be connected with a plug; The material of the box body for distribution boxes and switch boxes is generally made of steel plate or insulation board, but it is not advisable to use wooden materials; The distance between electrical boxes should not be too far. The distance between the distribution box and the switch box shall not exceed 30m. The horizontal distance between the switch box and fixed electrical equipment should not exceed 3 meters.

5. Mechanical requirements for distribution boxes.

The gaps between the doors and the shell of the distribution box must be consistent, with a gap of less than 1mm. When the gap length is greater than 1 meter, the uniformity difference should not exceed 1.5mm. The nameplate of each distribution box must be made of metal, which should include at least six items: product name, model, manufacturer name, main technical parameters, factory number, production date, etc. The nameplate should be fixed in a visible position on the front panel, and the specific position should be aesthetically pleasing and reasonable. The fixation should be firm. The box must be accompanied by the main circuit diagram, system diagram, schematic diagram, and secondary control diagram. The parameters in the circuit diagram must be consistent with the actual object and must be treated with plastic. A 2mm thick flame retardant transparent board should be embedded behind the box door.

The welding and bolt connection of the distribution box should be firm, and the welds should be uniform, smooth, without welding skin, welding penetration, air holes and other adverse phenomena; The connection of bolts should have flat, spring washers, and 2-5 exposed threads. The internal parts and opening edges of the distribution box should be flat and smooth, without burrs or cracks. The moving parts of the box should be flexible to open and close, and the coating or coating should not be damaged during the opening and closing process. The opening angle should not be less than 90 degrees. The door lock should be a concealed lock, and the door lock should be firm and reliable. There should be no obvious shaking after locking. The door hinges should be made of metal chrome plating. When the door length is greater than 1.2 meters, three hinges should be installed, and when it is less than 1.2 meters, two can be used. The hinges should have sufficient load-bearing capacity to ensure that permanent deformation will not occur when the load is four times that (not less than 10kg).

The thickness of the steel plate selected for the distribution box body shall not be less than 1.5mm, and the distribution box body shall be made of cold-rolled steel plate with a thickness of not less than 2.0mm. The thickness of the steel plate door and plate surface shall not be less than 2.0mm. The thickness of the back panel shall not be less than 3.0mm. The guide rail must be sturdy, and the structure of the distribution box should be complete and sturdy. At the same time, two connecting ears are welded on the lower left and upper right corners of the back of the non floor standing distribution box. The connecting ears are made of 40 * 4 flat steel, with a length of 10cm. The connection and assembly position of electrical components inside the box should be reasonable, and the number, size, shape, and installation method of reserved holes for incoming and outgoing lines should comply with the specific parameters of national standards, atlases, and design drawings. The reserved opening or tapping holes for the incoming and outgoing lines should have corresponding sealing components to ensure that they meet the three-level sealing requirements after the assembly of the incoming and outgoing lines.

6. Protection requirements for distribution boxes; The distribution box is required to operate under conditions of third level pollution, that is, the protection level of the distribution box should reach IP3X. All steel plates and profiles used in the box must undergo degreasing, rust removal, and phosphating treatment before spraying. Other metal parts must have anti-corrosion ability, otherwise anti-corrosion measures must be taken for treatment. All insulation in the distribution box must be self extinguishing materials. The distribution box must undergo various electrical performance inspections and experiments in accordance with GB05171-1992 and relevant national regulations and standards, and the manufacturer shall provide all inspection and experimental data and effective inspection and experimental reports to the supervisor of Party A. After the equipment enters the site, the handover test shall be carried out in accordance with the Electrical Equipment Handover Test Standard (GB50150) for Electrical Equipment Installation Engineering. Only after passing the test can it be accepted. The electrical performance of other distribution boxes not mentioned should meet the Quality Acceptance Specification for Building Electrical Engineering

7. All components inside the box should be selected strictly in accordance with the contract and the drawings provided by us. If there are any changes, we will notify you separately. Auxiliary components not specified on the drawings should be selected from qualified products of certified manufacturers. All components on the product should ensure that they meet the performance requirements, and the manufacturer should provide proof of origin, supplier qualifications, specifications and models, breaking capacity of circuit breakers, and proof documents of electromagnetic leakage protectors. The installation of components inside the box should be tight, without any slipping or damage to the coating, and anti loosening measures should be taken. The fasteners should be fully configured.

8. All boxes should be welded with a main grounding terminal on the box structure. The main grounding terminal should match the maximum grounding wire inside the grounding box, and a standardized grounding terminal symbol should be made at the grounding terminal. The busbar of the protective grounding system should be marked with yellow green color and PE letter throughout the entire length. The box should be equipped with a dedicated grounding bolt with a diameter of no less than 6mm connecting to the metal foundation. The metal plates, frames, all movable doors, isolation second layer plates, metal plates with charged conductors, doors with electrical appliances above 36V, and cover plates of the box must be reliably connected to the grounding terminals on the box using copper braided tin strips to ensure the continuity between the normally operating non charged metal parts in the box and the grounding system.

9. The color of the outer coating of the distribution box should be electrostatically sprayed according to the requirements of Party A. The coating should be firmly attached, uniform in color, without wrinkles, peeling, spots, missed spraying and other adverse phenomena. There should be no obvious color difference or reflection observed at a distance of 1 meter, and the surface should be flat and clean without any damage such as pits, scratches, etc. The other galvanized components used in the box should also be ensured to have no peeling, spots, plating leakage, rust or other adverse phenomena, and the external quality should meet the same requirements. There should be no debris or dust inside the box.

10. Nameplates and various markings; All provided nameplates, instructions, and warning signs must have a Chinese representation. The content of the nameplate should comply with relevant national regulations, and its material should be corrosion-resistant and wear-resistant metal material, which must be firmly attached to a prominent position of the equipment.

Article source: Jiangmen substation cabinet www.gdsandingdianqi.com