What are the requirements for the manufacture and installation of distribution cabinets in China?

The requirements for the manufacture and installation of power distribution cabinets in China are as follows:

Design and selection requirements:

Conforming to standards and specifications: The design, selection and production of power distribution cabinets should follow relevant national standards, such as GB7251 "Low-voltage switchgear" and GB50303 "Code for Quality Acceptance of Building Electrical Engineering", etc., and corresponding national standards, business standards or enterprise standards should be provided according to the standards on which they are based (enterprise standards should be higher than national standards or business standards).

Meet the requirements of the drawings: all technical indicators must meet the requirements of the design drawings. If it is necessary to change the electrical components and technical parameters, it must be filled in according to the requirements of the formal engineering data (negotiation) form and signed by the design institute, the construction unit, the supervisor, the construction unit and the factory representative.

Adapting to the use environment: according to the environmental characteristics of the place of use (such as temperature, humidity, altitude, whether there is corrosive gas or dust, etc.), power load and other factors, choose the appropriate type, specification and protection level of power distribution cabinet. For example, in a humid and dusty environment, cabinets with higher protection level should be selected; At high altitude, the influence of thin air on electrical insulation performance should be considered.

Cabinet and structure requirements:

Cabinet material: generally, cold-rolled steel plates conforming to national standards are adopted. Floor cabinets are usually made of 2.0mm thick cold-rolled steel plates, lighting distribution boxes and control boxes with sizes greater than or equal to 600mm are made of 2.0mm thick cold-rolled steel plates, and those with sizes less than 600mm are made of 1.5mm thick cold-rolled steel plates, and the second floor needs 2mm thick cold-rolled steel plates.

Structural strength of the cabinet: the cabinet should have sufficient mechanical strength and rigidity, be able to withstand various stresses during transportation, installation and use, and not be easily deformed or damaged. For example, the frame structure of the cabinet should be firm, and the welding place should be smooth and firm, without cracks, pores and other defects.

Protection grade: according to the different use environment, the protection grade of the cabinet should reach the corresponding standard. Common protection grades such as IP30, IP40, IP54, etc. The higher the number, the better the protection performance. For example, the protection level of outdoor distribution cabinets is generally higher than that of indoor ones.

Ventilation and heat dissipation: For power distribution cabinets with high calorific value, reasonable ventilation and heat dissipation structures, such as vents and heat dissipation fans, should be designed to ensure that electrical components operate within the normal working temperature range. Vents should be provided with protective nets to prevent foreign objects from entering the cabinet.

Door lock and seal: the door of the distribution cabinet should be flexible to open and close, and the door lock should be reliable to prevent unauthorized personnel from opening it. The door of the cabinet should be well sealed to prevent dust and water vapor from entering the cabinet.

Requirements for electrical components:

Component selection: The selected electrical components (such as circuit breakers, contactors, relays, fuses, switches, etc.) should meet the design requirements, and their rated voltage, rated current, short-circuit breaking capacity and other parameters should meet the actual use requirements. At the same time, products with reliable quality and well-known brands should be given priority, and components' certificates, Chinese instructions, CCC certification certificates, CCC test reports (compulsory certification) and commodity inspection certificates (imported products) should be provided.

Component installation: electrical components should be installed firmly to facilitate operation, maintenance and replacement. Sufficient electrical clearance and creepage distance should be kept between components to prevent arc discharge or short circuit fault. For example, for bare charged bodies, insulation protection measures should be taken.

Installation of heating elements: the installation of heating elements (such as tubular resistors, heat sinks, etc.) should consider their heat dissipation, and the installation distance should meet the requirements of the elements. Tubular resistors with rated power of 75W and above shall be installed horizontally, and shall not be installed vertically on the ground.

Wiring and wiring requirements:

Conductor selection: Select appropriate specifications and models of conductors according to the current and voltage level of the circuit. Generally speaking, the primary circuit can choose copper bus bar or insulated conductor with large cross section, and the secondary circuit usually chooses 1.5mm² (voltage circuit) or 2.5mm² (current circuit) black insulated conductor.

Wiring technology: wiring should be neat, beautiful, horizontal and vertical, and wires should not be crossed, twisted or twisted. Wires should be fixed firmly to avoid looseness or poor contact caused by vibration, external force and other factors. When passing through metal parts, measures should be taken to prevent the insulated conductor from being damaged, such as wearing rubber rings on the holes of the metal plate through which the conductor passes, winding pipes to wind the conductor, etc.

Wiring requirements: Wire connection should be firm and reliable, and bolt connection, crimping and welding can be adopted. The terminal should match the cross section of the conductor, and it is forbidden to press the conductor with different cross sections on one terminal (the conductor with the same cross section is less than 6 square millimeters, and only two conductors can be pressed on one terminal at most). The connection of the electrical circuit should meet the electrical safety standards, and the connection should be tinned to improve the conductivity and oxidation resistance.

Marking and numbering: The loop number of the conductor shall be marked on both ends, and the number shall be correct, legible and not easy to decolorize. Electrical components, terminals, etc. should also be identified, which should be complete, clear and firm, and the paste position should be clear and eye-catching.

Grounding and safety requirements:

Grounding protection: the power distribution cabinet must have good grounding protection, and the metal parts of the cabinet (including the mounting plate, bracket and metal shell of electrical appliances, etc.) should be reliably connected with the grounding trunk line. Grounding resistance should meet the requirements of relevant national standards, generally not more than 4 ohms.

Leakage protection: A leakage protection device should be installed for the circuit where leakage may occur. When leakage occurs, the power supply can be cut off in time to protect the safety of personnel.

Interlocking and protection device: when two or more power sources supply power, an interlocking device shall be installed between each power source and the contact switch (except those dispatched by the power supply department); Interlocking devices should be installed between the disconnector of 10 kV indoor complete equipment and the corresponding circuit breaker.

Safety warning: obvious safety warning signs should be set on the power distribution cabinet, such as "high voltage danger" and "no closing" to remind operators to pay attention to safety.

Installation and commissioning requirements:

Installation location: the distribution cabinet should be installed in a dry, well-ventilated, non-corrosive gas and dust, and avoid direct sunlight and rainwater immersion. The installation site should have a solid foundation, which can bear the weight of the distribution cabinet and ensure its stability.

Installation spacing: When multiple power distribution cabinets are installed in parallel, the spacing between cabinets should meet the requirements of relevant standards, so as to facilitate operation, maintenance and heat dissipation. For example, the distance between adjacent power distribution cabinets should not be less than 0.8m..

Debugging and testing: After installation, the distribution cabinet shall be fully debugged and tested, including electrical performance test, insulation resistance test, grounding resistance test, etc., to ensure normal functions and effective protection devices.