Handles three-phase power and typically connects to secondary loads such as motors or machinery. Equipped with larger three-phase circuit breakers. From the transformer's low-voltage side (0. 4kV), power is distributed to a main distribution panel (primary distribution box). From there, it is routed to individual building distribution boxes (secondary distribution boxes), which subsequently supply power to unit-level distribution boxes. Primary distribution systems consist of feeders that deliver power from distribution substations to distribution transformers. These boxes have inner and outer doors, powder-coated exteriors, and are designed for safety and aesthetic appeal, with rainproof tops for outdoor work.