Professional Answer: There are two primary classifications of earthing systems: equipment earthing and system earthing.

• Equipment Earthing refers to connecting the non-current-carrying metal parts of an electrical installation to the earth. This is a safety measure to prevent electric shock. Common methods include rod earthing, plate earthing, and strip earthing, chosen based on soil resistivity and available space.

• System Earthing involves connecting a specific point of the power system (like the neutral point of a transformer) to the earth. The most common systems are defined by IEC standards and include:

  • TN Systems: The neutral point is directly earthed at the source, and exposed conductive parts of the installation are connected to the earth via a separate protective conductor (TN-S), or a combined neutral and protective conductor (TN-C or TN-C-S).

  • TT Systems: Both the supply source and the consumer's installation are connected to separate earth electrodes. This is common in public distribution networks.

  • IT Systems: The supply source is isolated from the earth or connected via a high impedance. This is often used in industrial or critical applications where service continuity is essential, as a single earth fault will not immediately trip the system.