The primary distribution box refers to the main distribution box, typically located in the distribution room. Today, electrical systems are essential for homes and industries. 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. Medium. The criteria for a high-quality electric supply include a consistent voltage level, limited voltage fluctuations within acceptable limits, a stable frequency, the absence of detrimental harmonics, protection against power surges and lightning, among other factors. Each circuit is protected by its own circuit breaker.