What's the difference between "primary, secondary and tertiary distribution boxes"

The difference between primary, secondary and tertiary distribution boxes: \x0d\ 1. Primary distribution box: Three-phase power supply, grounding wire and neutral wire are introduced by transformer. \x0d\2。 Secondary distribution box: that is, from the power line of the primary distribution box to the vicinity of the power point. \x0d\3。 Three-level distribution box: it is the control cabinet of electrical equipment itself. \x0d\\x0d\ In large-scale distribution system, power supply is carried out in stages for power safety and convenience of maintenance. For example: a residential building. There are five units in total, so the main distribution box supplying power to the building is the main distribution box. Then the five branches are divided into five units through the primary distribution box, and the distribution box in each unit is a secondary distribution box. Then it is divided into several branches through the unit distribution box, and the distribution box in the household is the three-pole distribution box.