1) Generally, the incoming line of power distribution box adopts five wire system, that is, a, B and C three-way phase line (the general color is yellow, green and red), one way zero line (the color is light blue) and one way ground line (the color is yellow with green. 1) Generally, the incoming line of power distribution box adopts five wire system, that is, a, B and C three-way phase line (the general color is yellow, green and red), one way zero line (the color is light blue) and one way ground line (the color is yellow with green. ABB Mini Center Compact distribution board is the basis for development and growth in meeting all the demands for a successful future in residential, commercial, and infrastructure segments. The wide range of distribution boards enables each customer to select an individual and economical. Phase 3's Powersafe Sequential Mating Box controls the connection sequence of incoming / outgoing high current cable connections. With key (included) turn the Earth lock clockwise. The outgoing line from the low-voltage end of the transformer is 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. A distribution box is the heart of any electrical system. It takes the incoming power and safely distributes it to different circuits throughout your building. A distribution board, also known as a DB box, is like the central hub of an electrical system.