Summary of Three-Tier Power Distribution System: Primary: The main distribution panel, supplies power from the transformer. In a newly constructed residential area, a 10kV power line is introduced into the substation. 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. The terms primary, secondary, and tertiary distribution boxes are relative. From the transformer's low-voltage side (0. These boxes feature bottom entry and exit cables, front-opening doors, and main busbars connected with copper strips for optimal contact. Mainly play the role of distribution and aggregation.