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Overview of basic knowledge of distribution box and distribution cabinet

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The distribution box is divided into power distribution box and lighting distribution box, which is the last level equipment of the distribution system. The distribution box is to assemble the switchgear, measuring instruments, protective appliances and auxiliary equipment in a closed or semi closed metal cabinet or panel according to the electrical wiring requirements to form a low-voltage distribution device. During normal operation, the circuit can be connected or disconnected with the help of manual or automatic switch. In case of fault or abnormal operation, cut off the circuit or alarm with the help of protective appliances. The measuring instrument can display various parameters in operation, adjust some electrical parameters, and prompt or send signals for deviation from the normal working state. It is commonly used in various power generation, distribution and substation.

 

Classification according to the requirements of power supply system:

 

1) Primary power distribution equipment is collectively referred to as power distribution center. They are centrally installed in the enterprise's substation and distribute electric energy to lower level distribution equipment in different locations. This level of equipment is close to the step-down transformer, so it has high requirements for electrical parameters and large output circuit capacity.

 

2) Secondary power distribution equipment is a general term for power distribution cabinet and motor control center. The power distribution cabinet is used in occasions with scattered load and few circuits; Motor control center is used for occasions with concentrated load and many circuits. They distribute the electric energy of a certain circuit of the upper level distribution equipment to the nearby load. This level of equipment shall provide protection, monitoring and control for the load.

 

3) The final power distribution equipment is generally called lighting power distribution box. Far away from the power supply center, they are scattered small capacity distribution equipment

 

Distribution boxes are classified according to structural features and uses:

 

1) Fixed panel switchgear, often called switch board or distribution panel. It is an open switch cabinet with panel blocking. The front has protective effect, and the back and side can still touch the live parts. The protection level is low. It can only be used for centralized power supply in the substation in industrial and mining enterprises with low requirements for power supply continuity and reliability.

 

2) Protective (i.e. closed) switchgear refers to a low-voltage switchgear whose sides are closed except the mounting surface. The switch, protection, monitoring and control and other electrical components of the cabinet are installed in a closed shell made of steel or insulating materials, which can be reliably installed on or off the wall. No isolation measures can be taken between each circuit in the cabinet, or grounded metal plate or insulating plate can be used for isolation. Generally, the door is mechanically interlocked with the main switch. In addition, there is a protective platform type switch cabinet (i.e. console), which is equipped with control, measurement, signal and other electrical appliances. The protective switch cabinet is mainly used as the power distribution device on the process site. 3) Drawer type switch cabinet. This kind of switch cabinet is made of closed shell made of steel plate, and the electrical components of incoming and outgoing circuit are installed in withdrawable drawers to form a functional unit that can complete a certain type of power supply task. The functional unit is separated from the bus or cable by a grounded metal plate or a functional plate made of plastic to form three areas of bus, functional unit and cable. Isolation measures are also taken between each functional unit. Drawer type switchgear has high reliability, safety and interchangeability. It is a cutting-edge switchgear in technology. Most of the produced switchgear are drawer type switchgear. They are suitable for industrial and mining enterprises and high-rise buildings that require high power supply reliability as centralized control distribution centers.

 

4) Power and lighting distribution control box. Mostly closed vertical installation. Due to different use occasions, the enclosure protection grade is also different. They are mainly used as power distribution devices at the production site of industrial and mining enterprises.

 

Characteristics, types and functions of distribution box

 

1) It is convenient for management and maintenance in case of circuit failure.

 

2) Distribution box, distribution cabinet, distribution panel, distribution panel, etc. are complete sets of devices for centralized installation of switches, instruments and other equipment.

 

3) The commonly used distribution boxes are made of wood and iron plate.

 

4) Purpose of distribution box: of course, it is convenient for power shutdown and transmission, and plays the role of measuring and judging power shutdown and transmission.

 

Distribution box installation

 

1) The distribution box shall be made of non combustible materials, generally metal cold-rolled steel plate and 201 and 304 cold-rolled stainless steel plate, as well as the distribution box made of flame-retardant plastic.

 

2) Open distribution boards can be installed in production places and offices with low risk of electric shock.

 

3) Closed cabinets shall be installed in processing workshops, casting, forging, heat treatment, boiler room, carpentry room and other places with high risk of electric shock or poor working environment.

 

4) Enclosed or explosion-proof electrical facilities must be installed in hazardous workplaces with conductive dust or flammable and explosive gases.

 

5) All electrical components, instruments, switches and lines of the distribution box shall be arranged neatly, firmly installed and easy to operate; The cabinet (box) shall be free of dust, ponding and sundries.

 

6) The bottom surface of floor mounted cabinet (box) shall be 50 ~ 100 mm higher than the ground; The center height of the operating handle is generally 1.2 ~ 1.5m; There is no obstacle within 0.8 ~ 1.2m in front of the cabinet (box).

 

7) The protective wire is reliably connected.

 

  1. No bare electrified body shall be exposed outside the cabinet (box); The electrical components that must be installed on the outer surface of the cabinet (box) or on the distribution board must have reliable screen protection.
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