Sockets are typically installed in the third-level distribution box, directly supplying power to individual electrical devices while being protected by circuit breakers and leakage protectors.

Overview of Three-Level Distribution Boxes

First-Level Distribution Box (Main Distribution Box): This is the primary hub connected to the main power source. It contains main circuit breakers, isolation switches, leakage protectors, and measuring instruments like voltmeters and ammeters. Its role is to distribute power safely to second-level boxes and provide centralized monitoring and protection for the entire system . Second-Level Distribution Box (Sub-Distribution Box): Installed near large electrical loads or specific areas, it receives power from the first-level box and distributes it to third-level boxes. It typically contains branch circuit breakers and branch leakage protectors, ensuring protection and control for each branch circuit . Third-Level Distribution Box (Final or Switch Box): This is the end point of the distribution system, directly connected to electrical devices. It contains single-phase or small three-phase circuit breakers, isolation switches, and leakage protection devices. Sockets are installed here to provide power to individual appliances or groups of similar devices, ensuring that each socket is protected by its own breaker and leakage protector .

Function and Safety Considerations

• Direct Power Supply: Sockets in the third-level box allow flexible connection of movable or fixed electrical equipment .
• Protection: Each socket is typically connected through a leakage protection switch and a circuit breaker, following the principle of "one machine, one switch, one leakage, one box, one lock," which prevents multiple devices from being controlled by a single switch .
• Flexibility: Using cables from the second-level box, the third-level box can be positioned to suit the layout of the site, allowing easy expansion or adjustment of socket locations .
• Industrial and Residential Use: In industrial or high-load systems, sockets may be heavy-duty and rated for higher currents, while residential third-level boxes use standard single-phase sockets with RCBOs for individual circuits .

Summary

In a three-level distribution system, sockets are primarily located in the third-level distribution box, providing the final connection point for electrical devices. They are integrated with circuit breakers and leakage protection to ensure safety, flexibility, and compliance with electrical standards, while the first and second-level boxes focus on centralized distribution and branch protection .