Grounding (also known as earthing) connects an electrical circuit or equipment to the earth via a conductive path. Generally, grounding is categorized into three types: safety grounding, functional grounding, and lightning protection grounding.
It is important to distinguish "Common" (or "Common Ground") from "Ground." "Common" refers to the reference potential required for a circuit's operation, which is not always connected to the earth potential.
Safety Grounding
Safety grounding (protective grounding) is a critical safety measure designed to protect users and equipment from electric shock. It provides a low-impedance path for fault currents--such as those caused by insulation failure--to flow safely to the ground, triggering protective devices like breakers or fuses.
Functional Grounding
Functional grounding is used to ensure the stable operation of electronic equipment. It establishes a stable reference potential (typically zero volts) and serves as a return path for signals, helping to stabilize circuit performance and minimize noise interference.
Lightning Protection Grounding
Lightning protection grounding is designed to divert high surge currents from lightning strikes directly to the earth. This system protects facilities and critical electrical systems from catastrophic damage and ensures personnel safety.
IEC standards define specific symbols for grounding terminals to ensure proper identification and safety. The key symbols and their definitions are as follows:
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IEC 60417-5017 | Earth (Ground) Terminal | Indicates the connection point to the earth (ground). |
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IEC 60417-5019 | Protective Conductor Terminal | Identifies the terminal for connecting an external protective conductor specifically for protection against electric shock. |
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IEC 60417-5020 | Frame or Chassis Terminal | Indicates the connection point to the equipment's frame or chassis. |
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