What are the specifications of a three-level distribution box

A three-level distribution box system consists of primary, secondary, and tertiary boxes, each with specific configurations, protection measures, and installation requirements to ensure safe and efficient power distribution.Overview of Three LevelsPrimary Distribution Box (Level I)Acts as the main distribution point, directly connected to the transformer, typically handling 0.4kV power .Supplies power to secondary distribution boxes rather than directly to end-use equipment .Configuration: Includes main circuit isolation, main circuit breaker, main fuse, shunt isolation, and shunt leakage protection switch .Often equipped with copper busbars for optimal conductivity and may feature rainproof designs for outdoor use .Secondary Distribution Box (Level II)Serves as an intermediate panel, routing power from the primary box to specific zones, buildings, or floors .Configuration: Main circuit general isolation, main circuit fuse and circuit breaker, shunt isolation, and shunt fuse and circuit breaker .Typically features double doors, spray-painted exterior, and rainproof tops for outdoor installation .Supports multiple branch circuits to tertiary switch boxes while maintaining hierarchical distribution .Tertiary Distribution Box (Level III)The final junction box for electrical equipment, delivering power to individual devices or sockets .Configuration: Isolation and leakage protector for each connected device .Can be fixed or portable, ensuring individual circuit protection and adherence to the principle of “one machine, one switch, one leakage, one box, one lock” .Must connect only to its designated equipment without bypassing levels .Key Design PrinciplesHierarchical Distribution: No electrical equipment should bypass levels; each level must branch power according to the system hierarchy .Separate Circuits: Power and lighting circuits should be separated, with distinct branch circuits and switch boxes .Distance Limits: Maximum distance from distribution board to switch box should not exceed 30 meters; horizontal distance from switch box to equipment should preferably be under 3 meters .Environmental Safety: Install boxes in dry, ventilated, and normal-temperature locations, avoiding harmful gases, moisture, mechanical impact, or heat radiation .Maintenance Access: Provide sufficient space for two persons to work simultaneously, with no obstructions nearby .Protection MeasuresTwo-Level Protection: Leakage protection is installed at both the tertiary switch box and the upper-level distribution box to ensure safety .Circuit Isolation: Each level includes isolation switches and circuit breakers to prevent overloads and short circuits .Compliance: All boxes should meet construction electricity standards and safety regulations for temporary or permanent installations . This three-level distribution system ensures safe, reliable, and organized power distribution, particularly suitable for construction sites, large-scale projects, or complex electrical installations.