Circuit Breakers/Fuses: Automatically disconnect when there are overloads or short circuits. Residual Current Devices (RCDs): Detect ground faults and cut off power to prevent shock. Main Switch: Supplies on/off for the power of the. Simply put, a power distribution box acts as the central hub for routing energy from an incoming service line — typically supplied by a transformer or substation — to individual branch circuits. But what exactly is a power distribution box, and why is it so essential in our daily lives? The DB panel board controls the flow of electricity.