Primary distribution box: three-phase power supply, ground wire and zero wire are introduced from the transformer. Home / blog / Ultimate Guide to Distribution Boxes (DB Boxes): Types, Components, Applications, and How to Choose the Right One For procurement professionals, electrical contractors, and project managers, choosing the right Distribution Box (DB Box) is a critical decision that directly impacts. The distribution box can also be called a distribution board or an electrical panel. It is a centralized electrical unit designed to house switches, protection and distribution components. 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.