Kaitsemaandus

Kaitsemaandus, or protective earthing, is the practice of connecting exposed conductive parts of electrical equipment and installations to the earth. The goal is to keep these parts at earth potential and to provide a low-impedance path for fault currents, so that protective devices such as fuses or residual-current devices disconnect quickly and safe conditions are restored, reducing the risk of electric shock and fire during insulation faults.

In an installation, kaitsemaandus comprises the protective earth conductor, which runs from the main distribution point to metal enclosures, appliances and exposed conductive parts, as well as earth electrodes or a grounding system. Equipotential bonding connects extraneous conductive parts (for example metal pipes or framework) to the protective earth to limit touch voltage during faults. The system is designed and tested according to local and international standards; color coding commonly uses green-yellow for the protective earth conductor, as prescribed by many standards.

Different earthing network configurations exist, notably TN, TT and IT systems. In typical buildings, TN-S or TN-C-S configurations are common, where fault currents return via a network of earth and neutral conductors. A TT system uses a separate earth electrode at the installation with no direct earth connection to the supply, and IT systems keep the supply neutral isolated or high-impedance.

Regulatory requirements for kaitsemaandus depend on the jurisdiction, but European and international standards such as IEC 60364 and related EN standards guide design, installation, testing and maintenance of protective earthing. Regular inspection and periodic testing of earth continuity and protective devices are part of electrical safety practice.