Brief introduction of basic knowledge of low voltage distribution box

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With the continuous development of the construction of power grid system in China, the frequency of distribution box is higher and higher, and plays an increasingly important role in the whole power grid system, which plays a great role in the normal operation of the power grid system. As a kind of power equipment, distribution box connects relevant measuring instruments, protective appliances, switchgear and auxiliary equipment according to certain electrical wiring mode, so as to form a system. The system is fixed by metal box cabinet in closed or semi closed way, and it is generally installed on the low-voltage side of distribution transformer. Let's go into the world of distribution box, and learn the basic knowledge of the lower distribution box.


1. Concept


The distribution box is a low voltage distribution box which is composed of switchgear, measuring instruments, protective appliances and auxiliary equipment assembled in closed or semi closed metal cabinets or on screen. Among them, the measuring instruments mainly include electric energy meter, current transformer, etc. the protective apparatus mainly includes leakage protector, lightning arrester, fuse, etc; The switchgear mainly includes load switch, separator switch, circuit breaker, contactor, etc; Auxiliary equipment mainly includes capacitor, connecting wire, equipment shell, etc.


When the distribution box is in normal operation, the circuit can be turned on or off by means of manual or automatic switch. It is the control center for directing the reasonable distribution of power supply energy for various components in power supply line, and is the control link of reliable acceptance of upper power supply and correct feeding of load power, and also the key to obtain the satisfaction of users with power supply quality. It is the goal of the project to improve the operation reliability of power distribution box.


2. Purpose


As an important part of the whole power system, distribution box undertakes the important work of power energy control and distribution. Its working principle is as follows: under normal circumstances, the circuit can be closed or disconnected by automatic switch or manual switch to supply or cut off current. When the circuit fails, the circuit can be disconnected by protecting electrical appliances, Prevent the circuit from running normally and reduce the damage caused by the fault to the power system. Through the data displayed by the measuring instrument, the operation status of the equipment can be dynamically understood, some settings can be adjusted. When the data display is abnormal, it indicates that the power system is in abnormal operation state, and measures can be taken to adjust in time. Its use can be roughly summarized as follows:


(1) Reasonable distribution of electric energy


(2) Convenient opening and closing operation of the circuit


(3) It has a high level of safety protection, and can directly display the on state of the circuit


3. Classification


Because the protection level of metal distribution box is higher, it is commonly used for metal distribution box.


By structural characteristics and use:


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


(2) Protective (i.e. closed) switchgear refers to a low voltage switchgear which is closed on all sides except the mounting surface. The switch, protection, monitoring and control and other electrical components of the cabinet are installed in a closed enclosure made of steel or insulating materials, and the reliable wall or off wall installation. Isolation measures can be taken between each circuit in the cabinet, or grounded metal or insulating plate can be used for isolation. Generally, the door is mechanically interlocked with the main switch operation. In addition, there are protective type switch cabinet (i.e. console), which is equipped with control, measurement, signal and other electrical appliances. The protective switchgear is mainly used as the distribution device on the process site.


(3) Drawer type switch cabinet, which is made of steel plate, is made of closed shell. The electrical components of the incoming and outgoing circuit are installed in the withdrawable drawer, which constitute a functional unit capable of completing a certain type of power supply task. The functional unit is separated from the bus or cable by the grounded metal plate or plastic functional board, forming three areas of bus, functional unit and cable. Isolation measures are also available between each functional unit. Drawer type switch cabinet has high reliability, safety and interchangeability, and is a more advanced switchgear. Most of the switch cabinets refer to drawer type switch cabinet. They are suitable for industrial and mining enterprises and high-rise buildings with high reliability of power supply, and they are used as distribution centers for centralized control.


Power and lighting distribution control box. Most of them are closed vertical installation. The protection level of the shell is different due to the different use situation. They are mainly used as distribution devices in the production site of industrial and mining enterprises.

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