Glossary · Electrical engineering and control panels
Protective bonding
Also known as: Protective equipotential bonding, Equipotential bonding
German: Schutzpotentialausgleich
In electrical engineering, protective bonding is the connection of exposed conductive parts and extraneous conductive parts to the protective earth, so that no dangerous touch voltage can arise between them in the event of an insulation fault.
- Control panels
In one sentence
Protective bonding connects conductive parts to protective earth so no dangerous touch voltage can arise during an insulation fault.
Example
The machine frame, cabinet doors and mounting plate are connected to the PE bar with green-yellow conductors as part of the protective bonding circuit.
How it applies
- Engineering: IEC 60204-1 describes the protective bonding circuit of machines, including conductor cross-sections and connection of parts such as hinged doors. Functional bonding for EMC is a separate purpose, though it often uses the same metalwork.
- Commissioning: Continuity of the protective bonding circuit is verified by measurement as part of the electrical tests before handover.
- Documentation: Show the protective bonding in the circuit diagram and describe reconnection after maintenance. Maintenance instructions should require re-testing when protective conductors are disconnected, for example after replacing a motor.
Protective bonding vs. functional earthing
Protective bonding protects people from electric shock. Functional earthing serves signal quality and EMC. Protective conductors must never be removed or used only for functional purposes.