Series connection of three-level distribution boxes

Three-level distribution boxes should not be connected in series bypassing levels; each level must follow a hierarchical branching structure.Hierarchical Structure of Three-Level Distribution SystemsA three-level distribution system consists of:First-Level Distribution Box (Main Distribution Box): Installed near the power source, it receives electrical energy and distributes it to second-level boxes. It contains main circuit breakers, leakage protectors, voltmeters, and ammeters for centralized monitoring and control .Second-Level Distribution Box (Sub-Distribution Box): Receives power from the first-level box and distributes it to third-level boxes. It typically contains branch circuit breakers and leakage protectors to manage and protect each branch circuit .Third-Level Distribution Box (Switch Box): Directly supplies power to electrical equipment. Each third-level box should control only one piece of equipment or a group of similar equipment, following the “one machine, one switch” principle .Connection PrinciplesBranching, Not Series: Power distribution should follow a branching hierarchy. The first-level box can supply multiple second-level boxes, and each second-level box can supply multiple third-level boxes. However, direct series connections that bypass levels are not allowed, as this compromises the structural integrity and safety of the system .Equipment Safety: All distribution boxes and connected equipment must be properly grounded. Protective devices like circuit breakers and leakage protectors must be installed at each level to ensure personnel and equipment safety .Distance and Layout: Distribution distances should be minimized. The main distribution box should be near the power source, second-level boxes near concentrated loads, and third-level boxes close to the equipment they control, typically within 3 meters .SummaryWhile three-level distribution boxes can supply multiple downstream boxes, they cannot be connected in series in a way that bypasses the hierarchical levels. Each level must maintain its role in the branching structure to ensure safety, proper protection, and compliance with electrical standards .