The Three Levels of Distribution Boxes

The primary distribution box receives the incoming three-phase power supply, ground wire, and neutral wire directly from the transformer. The secondary distribution box draws power from the primary distribution box's supply lines to provide temporary power. The tertiary distribution box serves as the dedicated control cabinet for the specific electrical equipment being utilized during construction.

 

The primary distribution box is typically designed to suit the specific conditions of a construction site. A complete set of primary distribution box units can form a comprehensive three-tier electrical protection system for construction operations, thereby achieving the objective of "one machine, one switch" protection. The main busbars within the primary distribution cabinet utilize copper busbar connections to ensure excellent contact; furthermore, the cabinets feature an internal metering system, offering both safety and aesthetic appeal.

 

The secondary distribution stage extends from the primary distribution box's supply lines to the vicinity of the actual power consumption points, facilitating the normal switching on and off of circuits. It incorporates protection functions against short circuits, overloads, and ground faults. These units must be installed at a height of 1.5 meters above the ground; typically, each unit is responsible for supplying power to a specific zone. This system is well-suited for construction site power requirements and, when integrated with other components, contributes to the overall three-tier electrical protection system and provides secondary-level ground fault protection.

 

The tertiary distribution box functions as the dedicated control cabinet for the specific electrical equipment itself. It can be installed and utilized in either a fixed or mobile configuration. A strict requirement applies at this level: "one machine, one ground fault protector"-meaning that multiple devices must not be daisy-chained together, and a single switching device must not be used to control two or more pieces of electrical equipment (including power outlets).