The application of miniature circuit breaker (MCB), the main electrical component installed in modern lighting distribution box, is summarized.

       1 Purpose of lighting distribution box

       The lighting distribution box is widely used in various buildings, squares, stations, industrial and mining enterprises and other places as the terminal electrical equipment of the distribution system.

       2 Box structure

       The lighting distribution box is structurally divided into two types according to the installation method: closed suspension type (open installation) and embedded type (concealed installation). The main structure is divided into box shell, panel, mounting bracket, neutral bus bar, grounding bus bar and other components. There are opening holes for operating the main switch and shunt switch on the panel. If it is not necessary to install all shunt switches, the opening hole can be partially closed with a sealing plate. The knock-out holes for the incoming and outgoing lines are placed on the upper and lower sides of the box shell. There is also a long round knockout hole on the back, which can be used after tapping according to the user's needs.

The lighting distribution box can be divided into steel box, stainless steel box, iron box and plastic box according to the material of the box.

       3 Main electrical components in the box and their protection functions

       3.1 Miniature circuit breaker (MCB)

       It is used as the main switch of incoming line or outgoing line sub-switch to provide overload and short circuit protection for distribution lines.

       3.2 Disconnector

       It is usually used as an incoming switch for power supply opening and closing isolation.

       3.3 Leakage protector

       Generally, the leakage action current is 30mA for personal electric shock protection.

       3.4 Surge protective device (SPD)

       It is used to limit the lightning overvoltage conducted from the power line.

       4 Application and safety and reliability of lighting distribution box

       As the terminal distribution equipment, the lighting distribution box has a large quantity, and its safety and reliability are related to thousands of households, so the selection should be very careful.

       4.1 Select qualified and authentic products

       At present, there are many fake and shoddy products in the lighting distribution box market. The short circuit explosion of the box circuit or other electrical faults that directly affect life and work often occur.

       Therefore, qualified and authentic products conforming to the national standards should be selected. It is an important part that the electrical components in the box should adapt to the controlled electrical equipment and have complete protection functions.

       4.2 Correctly design the electrical system of the distribution box according to the national specifications

For example, the national standard Code for Design of Residential Buildings (GB50096-1999) clearly stipulates that "each residential building shall be equipped with a main power circuit breaker, and the switching appliances that can disconnect the phase line and neutral line when available shall be used." It also stipulates that "except for the air conditioning power socket, other power socket circuits shall be equipped with leakage protection devices" and "the main power incoming circuit breaker of each residential building shall have leakage protection function" and the national standard Code for Design of Lightning Protection of Buildings (GB50057-94) also has specific provisions for the installation of surge protective devices, which must be implemented, because it is an important means to prevent and reduce the harm of electrical accidents, which is related to personal and equipment safety.