After stepping down the voltage through the transformer's low-voltage side (0. 4kV), power distribution is achieved through three levels of distribution boxes: the main distribution board, secondary distribution boards, and tertiary distribution boards. You know those ubiquitous green, square metal boxes? You probably pass a dozen a day and barely even notice them. Maybe you have one in your front yard, or there's one down the street. In a newly constructed residential area, a 10kV power line is introduced into the substation. These boxes feature bottom entry and exit cables, front-opening doors, and main busbars connected with copper strips for optimal contact. They also include metering systems, ensuring.