External Power Connection for Container Houses

External power connection for container houses must adhere to professional standards to ensure safety and compliance, primarily involving key aspects such as circuit layout, distribution box configuration, and grounding protection.

1. Circuit Layout and Connection

The external power supply for container houses is typically introduced from the low-voltage output of an external transformer, requiring a three-phase five-wire system (yellow-green-red for the three-phase lines, light blue for the neutral line, and yellow-green with a stripe for the protective zero line). After the circuit enters the main distribution room from the transformer's low-voltage output terminal, the neutral line must be grounded and connected to the first-stage residual current device (RCD) through a main disconnect switch (which must have a clear breaking point). The protective zero line (PE line) must be led out from the RCD and connected to the grounding terminal of the container house, forming a complete protective circuit.

2. Distribution Box Configuration and Hierarchy

The power distribution system must be set up hierarchically, including a main distribution box, sub-distribution boxes, and final switch boxes.

• Main Distribution Box: As the core node for power introduction, it must be equipped with a main disconnect switch, a first-stage RCD, and branch disconnect switches. The neutral line (N line) and the protective zero line (PE line) must be strictly separated to prevent mixed connections that could lead to RCD failure.
• Sub-Distribution Box: It draws three-phase lines and the neutral line from the main distribution box and distributes them to various electrical circuits through a second-stage RCD. The sub-distribution box must have an independent PE terminal block to ensure reliable connection of the protective zero line.
• Final Switch Box: It directly controls electrical equipment and must be equipped with a disconnect switch, an RCD, and an overload protection device. Single-phase equipment uses a single-pole switch, while three-phase equipment uses a three-pole switch to ensure rapid power cutoff in case of equipment failure.

3. Grounding and Safety Protection

The grounding system of container houses is crucial for ensuring electrical safety.

• Protective Zero Connection (PE Line): All metal casings and non-live conductors must be reliably grounded through the PE line to prevent the casing from becoming live in case of equipment leakage.
• Repeated Grounding: Additional grounding devices must be installed at the main distribution box, sub-distribution boxes, and the end of the circuit to reduce grounding resistance and enhance safety.
• Equipotential Bonding: Metal components inside the container house (such as steel frames and doors and windows) must be connected with braided soft copper wires to form an equipotential body, preventing electric shock risks caused by potential differences.

4. Special Scenarios and Considerations

• Mobility Requirements: If the container house needs to be frequently relocated, detachable distribution boxes and flexible cables must be used for quick disassembly and assembly.
• Environmental Adaptability: In humid or corrosive environments, waterproof and dustproof distribution boxes and cables must be selected, and their insulation performance must be regularly inspected.
• Compliance Verification: After power connection is completed, insulation resistance tests, grounding resistance tests, and RCD tests must be conducted to ensure the system complies with standards such as the "Technical Code for Safety of Temporary Electrification on Construction Sites" (JGJ46).