1 What are the three levels of a three-level distribution box

A three-level distribution box consists of primary, secondary, and tertiary levels, each serving distinct roles in power distribution from the transformer to end-use equipment.Primary Distribution BoxThe primary distribution box is the main distribution point connected directly to the transformer, typically receiving 0.4kV three-phase power from the low-voltage side of the transformer . It generally does not supply power directly to end-use equipment but distributes electricity to secondary distribution boxes. Key components include isolating switches, circuit breakers, and residual current devices (RCDs) to ensure overall circuit safety . This level is designed for centralized control and protection of the entire site or project.Secondary Distribution BoxThe secondary distribution box serves specific buildings, floors, or areas, distributing three-phase power to intermediate loads such as motors or machinery . It typically contains larger three-phase circuit breakers and may include dual-door protection and durable coatings for outdoor use. This level ensures safe operation of intermediate power loads and implements two-level protection, meaning leakage protection is installed both at the secondary and tertiary levels .Tertiary Distribution BoxThe tertiary distribution box is the final distribution point, supplying 220V single-phase power directly to end-use devices or household systems . It is designed for local control, with strict safety standards such as "one device, one circuit breaker, one RCD, and one box" to prevent electrical hazards. Tertiary boxes can be fixed or portable, providing independent circuit protection for each device and completing the three-level protection system .SummaryThe three-level distribution system ensures efficient power management, safety, and reliability: the primary box handles centralized distribution, the secondary box manages intermediate loads, and the tertiary box delivers power safely to individual devices or households. This structure is widely used in residential, construction, and industrial projects to maintain organized and protected electrical distribution .