päämaadoituspunktista

Päämaadoituspiste, or grounding point, is the point on the earth or on a structure where a metallic or conductive part of an installation is connected to the ground. The purpose of a grounding point is to provide a low‑resistance path for fault currents to return safely to earth, thereby protecting people, equipment and improving the overall safety of electrical and other hazardous systems.

The most common types of grounding points are shown in many national standards. For electrical installations a separate grounding electrode—typically a driven rod, plate, or mesh—is buried in the earth and connected to the system metal via a grounding conductor. In electromechanical, radio frequency and metallic enclosure installations, the grounding point may be a metal stud, a weld claw, or a dedicated Earthpoint. In many industrial settings a ground busbar provides a single, common reference point from which all other grounding conductors are distributed.

In accordance with national and international codes (e.g., IEC 60364, NFPA 70), the grounding point must have a characteristic impedance below a specified value (generally 25–40 Ω for electrical work). Materials used for the electrode must be durable against corrosion, often stainless steel, copper or galvanized steel. The size of the conductor depends on the anticipated fault current and is calculated from the worst‑case short‑circuit current.

Grounding points are also used in accordance with the 30 V rule for low‑voltage electronics and to reduce electromagnetic interference (EMI) by keeping the return current from entering a user‑space circuit. Proper selection, installation, inspection and maintenance of the grounding point are essential for compliance with safety regulations and for the reliability of telecommunications, power distribution, and safety cable systems.