Glossary · Electrical engineering and control panels
Ground loop
Also known as: Earth loop
German: Masseschleife
In electrical engineering, a ground loop is an unwanted current path formed when a signal circuit or cable shield is connected to ground at more than one point with different potentials, so that equalizing currents flow and disturb signals.
- Control panels
In one sentence
A ground loop arises when circuits are grounded at points with different potentials, letting equalizing currents disturb signals.
Example
A 4–20 mA signal shows a 50 Hz ripple because the transmitter and the analog input card are grounded in different buildings; a signal isolator removes it.
How it applies
- Engineering: Countermeasures include Galvanic isolation of signals, a low-impedance equipotential bonding system so potentials stay equal, and a deliberate shield grounding concept. Grounding shields at both ends is common for EMC, but requires good equipotential bonding.
- Troubleshooting: Symptoms are mains-frequency noise, offset in analog values and communication errors that change with plant load.
- Documentation: Describe the grounding and shielding concept in the installation manual and the plant's electrical documentation, including where signal references are grounded. Never solve ground loops by disconnecting protective earth conductors; manuals should say so explicitly.
Ground loop vs. protective earth
The Protective earth (PE) conductor protects people from electric shock and must never be interrupted. Ground loops are a signal-quality problem solved in the signal path, not by removing protective connections.