Differences Between Enclosure Grounding and Protective Grounding

1. Protective Grounding

• Strict grounding resistance requirements (usually ≤ 4Ω).
• Must be reliably connected to the protective grounding wire (PE wire) of the power supply system.
• Commonly used in low-voltage power distribution systems (e.g., TN-S, TT systems).

2. Enclosure Grounding

• Safety protection: Similar to protective grounding, it prevents electric shock from electrified enclosures.
• Electromagnetic shielding: To suppress electromagnetic interference (e.g., grounding of the enclosure of electronic equipment).
• Static discharge: To avoid static accumulation (e.g., cabinets of communication equipment).

• Metal enclosures of equipment, cabinets, shielding layers, etc.
• May be independent of the grounding of the power system (e.g., signal ground, anti-static ground).

• Grounding resistance may be more flexible (e.g., interference-proof grounding resistance ≤ 10Ω).
• May use separate grounding electrodes (e.g., lightning protection grounding for communication equipment).

Key Differences

Connections and Overlaps

• Overlap in safety functions: The enclosure grounding of power equipment is usually part of protective grounding.
• Special scenarios: For example, the enclosure of a frequency converter needs to achieve both protective grounding (for safety) and shielding grounding (for anti-interference). In such cases, separate grounding systems should be set up but ultimately share a common ground.

Precautions

• If equipment is only equipped with enclosure grounding but not connected to the protective grounding system (e.g., PE wire), it may not reliably cut off the power supply in case of a short circuit, posing a safety hazard.
• When the enclosure grounding of electronic equipment (e.g., anti-static grounding) needs to be separated from protective grounding, equipotential bonding should be adopted to avoid potential differences.