Wiring identification in power distribution cabins ensures clarity, safety, and traceability by using unique, readable, and consistent labeling for all wires.

Core Principles

1. Uniqueness: Every wire in a power distribution cabinet must have a unique identifier. Even wires in different circuits must be distinguished using prefixes, partitions, or circuit numbers to prevent confusion and misoperation .
2. Readability: Wire numbers should be clearly legible, using appropriate fonts (e.g., Song or Kai typeface) and sizes based on wire thickness and location. Main power wires typically use 10–12 point font, while secondary control wires use 8–10 point font. The color of the marking should contrast with the wire or cabinet background for easy visibility .
3. Continuity: Wires in the same functional circuit should be numbered consecutively. For example, control circuits start from "1" and increment sequentially, while main circuits follow phase sequence plus serial numbers .
4. Correspondence: The same wire number must appear at both ends of a wire. For wires crossing cabinets or terminal blocks, additional information such as terminal or cabinet numbers should be included (e.g., "103-TB2-04" indicates wire 103 connected to terminal 04 of terminal block TB2), .

Numbering and Labeling Rules

• Letter Marking: Uppercase letters indicate the system or component the wire belongs to.
• Number Marking: Arabic numerals indicate the serial number of wires within the same function. For multiple circuits, the circuit number is prefixed (e.g., 1-01, 2-01) to distinguish wires .
• Main vs. Control Circuits: Main circuits (primary power) are numbered with component number, phase sequence, and serial number, while control circuits (secondary circuits) follow a simpler sequential numbering .

Benefits

• Safety: Proper identification reduces the risk of accidental contact or misconnection.
• Maintenance Efficiency: Technicians can quickly trace circuits and perform repairs or modifications.
• Operational Clarity: Clear labeling ensures correct connections and prevents misoperation during system upgrades or troubleshooting .

Implementation

Standards such as NFPA 70 (National Electrical Code) and internal guidelines like those from Lawrence Livermore National Laboratory provide frameworks for numbering and labeling electrical equipment, ensuring consistency across panels, transformers, and distribution systems . By following these principles, power distribution cabins maintain organized, safe, and traceable wiring systems, which is critical for both operational reliability and personnel safety.