A distribution board (also known as panelboard, breaker panel, or electric panel) is a component of an electricity supply system that divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit in a common enclosure normally, a main switch, and in recent boards, one or more. Main distribution board function. Power distribution is a system, consisting of a main distribution board (mdb), sub main distribution boards (smdbs) and final distribution boards, by which the electrical energy is transmitted via branches to reach the exact end user an mdb is a panel or enclosure that houses the fuses, circuit breakers and ground leakage protection units where the electrical energy, which is used to.