aardings

Aardings, or grounding, is the intentional connection of electrical installations to the earth to establish a common reference potential and provide a low-resistance path for fault currents. This reduces shock risk, stabilizes voltages during faults and transient events, and helps ensure that protective devices operate reliably.

An aardings system typically comprises an earth electrode or electrode array installed in the soil, an earth conductor that runs from the main distribution board to the electrode, and protective earth conductors that connect exposed metallic parts of equipment to the earth. Bonding between different conductive parts ensures a single potential and reduces touch voltage. The arrangement and sizing of conductors, electrodes, and bonding are determined by local electrical codes and the expected fault current.

Various earthing arrangements are used worldwide, including TT, TN, and IT systems. In a TT system, the installation is connected to a local earth electrode and relies on the utility's earth for fault current return; in a TN system, the protective earth is bonded to a network earth at the supply and to the equipment; in an IT system, the installation is electrically isolated from earth or connected with high impedance, which limits fault current. The choice of system affects safety, fault current path, and how protective devices operate.

Standards such as IEC 60364 and regional codes govern design, installation, and testing of aardings. Earth impedance is typically measured to verify adequacy, using methods such as the fall-of-potential (three-point) technique. Target values depend on the installation type and local requirements, but the goal is a low-impedance, reliable path to earth.

Maintenance includes verifying connections, inspecting for corrosion, and re-testing earth resistance after significant changes or soil condition shifts to maintain safety and performance.