Primary distribution box: three-phase power supply, ground wire and zero wire are introduced from the transformer. A feeder usually begins with a feeder breaker at the distribution substation. It takes electricity from the main source and safely sends it to different circuits in a home, office, or industrial setup. Without it, managing power would be messy, unsafe, and inefficient. From the transformer's low-voltage side (0. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 33 kV. Electrical distribution boxes are used in commercial and residential buildings and are part of the electrical system, also known as switchboards.