In multi-core control cables, the "water line" (usually referring to the yellow-green dual-colored wire or a dedicated grounding identification wire) is an important core with specific functions. Its core role is safety grounding, and its specific functions and significance are as follows:
1. Safety protection to prevent electric shock risks
Control cables are commonly used for signal transmission or auxiliary power supply in industrial equipment and electrical control systems. The water line serves as a protective grounding wire (PE line), which can connect potentially live components such as equipment metal casings and cable shielding layers to the ground.
①When the internal insulation of the equipment fails, causing the casing to become live, the water line can quickly conduct the current to the ground, preventing electric shock accidents when a person comes into contact with the equipment.
②Meanwhile, over-current protection devices (such as circuit breakers) will cut off the power supply due to the action of short-circuit current, further ensuring safety.
2. Suppress electromagnetic interference to ensure signal stability
Multi-core control cables often transmit weak control signals (such as sensor signals and command signals) and are susceptible to external electromagnetic interference (such as high-frequency noise generated by motors and frequency converters).
①If the water line is connected to the cable shielding layer and grounded, a "shielding grounding loop" can be formed, which will guide the interference signal into the ground through the water line, reducing the interference to the internal signal line and ensuring the accuracy and stability of the control signal.
②In certain scenarios, the water line can also serve as an "equipotential bonding wire" to balance the potential difference between devices at both ends of the cable, thereby preventing stray current interference signals caused by the potential difference.
3. Clearly labeled and compliant with safety standards
International and national electrical standards (such as IEC, GB, UL, etc.) have mandatory requirements for the identification of protective grounding wires, usually in yellow green dual color (yellow green stripes), and are not allowed to be used for other purposes.
The setting of water lines in multi-core control cables can visually distinguish the grounding circuit, facilitate quick identification during installation and maintenance, ensure correct connection of the grounding system, and comply with electrical safety regulations.
4. Summary
The water line in multi-core control cables is a critical component for ensuring equipment and personnel safety. Its core function is safety grounding, while also suppressing electromagnetic interference and clearly identifying grounding circuits. It is an indispensable safety protection line in industrial electrical systems.
