What do the primary, secondary, and tertiary boxes of a distribution box mean? This is a relative issue. Let's make a hypothesis: a newly built residential area introduces a 10kV incoming line and builds a distribution room. The outgoing line from the low-voltage end of the transformer is 0.4kV to the distribution cabinet (primary distribution cabinet), then the outgoing line is led to the distribution box (secondary distribution box) in each building, and finally the outgoing line is led to the distribution cabinet (tertiary distribution) in each unit building, and finally enters the household.

Generally, first level distribution does not allow direct use of electrical equipment, and second level distribution will be by power equipment because it is three-phase electricity, while third level distribution is mains electricity (220V). As for the equipment inside, there are certain differences: the first level distribution cabinet generally has isolation switches, circuit breakers, leakage protectors, etc., the second level contains a large three-phase circuit breaker, and the third level contains a single-phase circuit breaker. Of course, this is an example of selecting equipment based on different electricity loads. Next, let's learn in detail the functions and uses of primary, secondary, and tertiary power distribution.

(1) Primary distribution box
The construction power distribution cabinet is designed specifically for the special situation of the construction site and complies with the relevant construction electricity specifications and standards of the construction department. The complete set of products can form a complete three-level protection system for construction electricity, achieving the goal of one machine, one switch, and one protection, which is very suitable for various standard engineering applications. The first level cabinet adopts bottom in and bottom out lines, with front doors open. The main busbar is connected by copper bars, with good contact. It comes with a measuring system inside, which is safe and beautiful. The rainproof box top is suitable for outdoor work.
(2) Secondary distribution box
Suitable for construction electricity on construction sites, it is specifically designed for the special situation of the construction site and complies with the relevant construction electricity standards of the construction department. The complete set of products can form a complete three-level protection system for construction electricity, achieving the goal of one machine, one switch, and one protection. The secondary box adopts an inner and outer door design, with a spray painted exterior. It is safe and aesthetically pleasing, and the rainproof top of the box is suitable for outdoor work.

(3) Third level distribution
A distribution box is installed under the main distribution box, and a switch box is installed under the distribution box. Electrical equipment is installed under the switch box, forming a three-level distribution. "Two level protection" mainly refers to the use of leakage protection measures. In addition to installing leakage protectors in the final switch box, a first level leakage protector should also be installed in the upper level distribution box or main distribution box, forming a two-level protection overall.
The principle of "one machine, one switch, one leakage, one box, one lock" strictly prohibits the same switchgear from directly controlling two or more electrical devices (including sockets).
(4) Temporary construction electrical boxes are generally classified into three levels of protection according to relevant national requirements
First level distribution box: can be understood as the main distribution box of theconstruction site or project (usually only one);
Secondary distribution box: distribution boxes for each floor or building (according to actual conditions);
Third level distribution box: refers to the final junction box of each electrical appliance, which can be movable and fixed. Remember that the leakage protection switch is the last one, and connect the electrical appliance from the leakage protection switch. The requirements for the distribution box can be based on the power consumption plan of the project, and if not, you can go to a sample construction site to see (such as large projects, which are usually very formal).