As for the equipment inside, there are certain differences: the first level distribution cabinet generally has isolation switches, circuit breakers, leakage protectors, etc. Primary power distribution: temporary electricity is in a place where the construction needs electricity, that is, from the transformer into the three-phase power supply, ground wire, neutral line. From the transformer's low-voltage side (0. 4kV), power distribution is achieved through three levels of distribution boxes: the main distribution board, secondary. Primary Distribution Box: Serves as the main distribution box for a construction site or project (usually only one). It is specially designed for the special situation of the project construction site and meets the relevant construction power specifications and standards of the construction department.