jordningen

Jordningen, or grounding (earthing), is the practice of connecting an electrical installation to the earth to establish a common reference potential and provide a low-impedance path for fault currents. The primary purpose is safety: to limit touch voltages, enable protective devices to operate quickly, and reduce the risk of electric shock and fire.

In electrical systems, jordningen serves to route fault currents away from people and equipment. A stable earth reference also helps stabilize voltage levels during transient events and supports lightning protection schemes. Protection relies on a low-impedance path to earth so that fuses or circuit breakers can interrupt the fault current promptly.

There are several system approaches, including TT, TN, and IT. In a TT system, the installation has its own earth electrode, while the utility earth is separate; protective earth is connected to this local electrode. In TN systems, protective earth conductors are linked to the neutral at the source, with various subtypes (TN-S, TN-C, TN-C-S) describing how conductors are arranged. An IT system keeps the supply neutral isolated or connected through a high impedance, which can improve continuity of service in case of a fault, at the cost of slower fault indication.

Key components include ground electrodes (rods, plates, or mats), main earth conductors, and bonding connections that ensure equipotentiality between metal parts. Earth resistance and impedance are measured to verify effectiveness, typically using Earth resistance tests and continuity checks. Standards such as IEC 60364 and related regional regulations govern design, installation, and testing of jordningen to ensure safety and reliability.