Primary Distribution Box: Serves as the main distribution box for a construction site or project (usually only one). Let's make an example for clarity: A newly constructed residential area introduces a 10kV power line to a substation. From the transformer's low-voltage side (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. Distribution boxes, often called breaker boxes or fuse boxes, are basically the central hub where electricity from your main supply gets divided into different circuits.