What earthing means
Earthing establishes an electrical connection to the ground through electrodes and conductors. In protection of people, it forms part of a system that limits hazardous voltages and enables protective devices to operate according to the installation’s earthing arrangement. It is not simply connecting a wire to any nearby metal object.
Related concept: Electrical risk.
Parts of the system
Distinguish the electrode, earthing conductor, main earthing terminal, protective conductors and equipotential connections. Each has a function. Continuity from an accessible exposed conductive part to the intended system is essential: a satisfactory electrode resistance measurement alone will not reveal a broken protective conductor in a machine.
Earthing and disconnection work together
Effectiveness depends on the electrical arrangement and protective devices. It is incorrect to claim that earthing eliminates all voltage or that an RCD makes it unnecessary. In circuits requiring a protective conductor, continuity must be maintained and the conductor must be sized and protected for foreseeable conditions.
What is verified
Inspection must identify connections, deterioration, corrosion, modifications and the results of appropriate measurements. Values are interpreted against the design and protection mechanism, not a universal number of ohms. Record measurement conditions and locations so results can be compared and changes that may compromise safety detected.
Hypothetical example
A machine has a correct earthing connection in the building, but the extension lead being used has no protective contact. The main electrode does not compensate for this interruption. Continuity and supply compatibility must be resolved before use; adding an improvised clamp to a pipe is not a valid repair.
Limits and safe working
Permanent protective earthing differs from the earthing and short-circuiting used for certain electrical work. It does not authorise live work. Checks and modifications require competent personnel, safe procedures and compliance with local requirements. The cited REBT applies to low-voltage installations in Spain, with specific conditions according to use.
