Wiring in high-voltage distribution box

High-voltage distribution boxes should be wired using a structured approach that ensures proper phase connection, grounding, insulation, and compliance with safety standards. Wiring ConfigurationHigh-voltage distribution boxes typically use a five-wire system for incoming lines: three-phase lines (A, B, C), a neutral line, and a grounding line. The phase lines are usually color-coded (yellow, green, red), the neutral line is light blue, and the grounding line is yellow with green stripes.

Outgoing lines are configured according to load requirements: single-phase 220V loads use one phase, one neutral, and one ground; three-phase 380V loads use all three phases plus grounding, with a neutral if local control is needed. Special two-phase 380V equipment requires any two-phase lines plus grounding.

Connection Components

Incoming lines are connected through air switches, circuit breakers, or knife switches, with the neutral and grounding lines pressed to their respective terminal blocks. For higher reliability, high-voltage cable junction boxes may be used, which are fully insulated, sealed, and capable of operating in harsh conditions. These boxes provide flexible connection options and can replace traditional ring main units in many scenarios.

Installation Method

Distribution boxes should be firmly fixed, horizontally and vertically aligned, with vertical deviation not exceeding 3mm. Wall-mounted boxes are secured using expansion bolts or embedded wood bricks, while concealed installations are embedded in walls with concrete filling for stability. The edges should be close to the wall, and contact surfaces coated with anti-corrosion paint.

Spiral fuses, if used, require the power line to connect to the middle contact terminal and the load line to the threaded terminal.

Grounding and Safety

Proper grounding is critical. High-voltage modules, such as the Vanner HVDM, include grounding busbars and pre-charge circuitry to safely manage capacitive loads. Capacitive discharge should reduce voltage to safe levels (e.g., 50 VDC) within minutes after disconnecting the system.

High-voltage contactors and fuses must be rated according to the system's voltage and current specifications.

Standards and Compliance

All wiring and installation must comply with local electrical codes, IEC standards, and EN-SFS 6000 series standards. Deviations from standard procedures require written approval. High-voltage connections should also follow the grid operator's specifications and connection contracts, detailing connection points, delivery time, and method.

Practical Tips

Use fully insulated junction boxes for outdoor or harsh environments. Ensure cable trenches and anchor bolts are correctly dimensioned for secure installation. Verify grounding busbar connections and pre-charge circuits before energizing the system.

Follow manufacturer instructions for high-voltage modules and panel boxes. Always perform wiring and installation under professional supervision to ensure safety and compliance. By following these wiring methods, high-voltage distribution boxes can be installed safely, reliably, and in compliance with technical standards.