An earth-fault trip calls for review of the trip unit event, circuit configuration, connected load and protection scheme. Actual ground leakage or insulation failure can be present, while CT configuration or wiring errors can also affect some schemes. Treat the event as a potentially serious electrical hazard.
What the symptoms may mean
These observations help organize the investigation. They do not prove the root cause.
| Observation | Possible cause | Useful evidence |
|---|---|---|
| Earth fault indicated after recent cable work | Possible cable or termination damage | Work permit, cable history and fault record |
| Trip coincides with a particular feeder or load | Downstream circuit fault possibility | Operational log and feeder identification |
| Problem follows CT or breaker work | Protection sensing or wiring configuration | Approved CT schematic and commissioning results |
| Trip occurs intermittently | Intermittent insulation or process-dependent issue | Time-stamped events and load conditions |
Understanding the possible causes
Ground fault is not the same as general overload
Electronic ACB trip units can have distinct protection functions for overload, short-time, instantaneous and ground-fault events. The event code matters more than an informal statement that the breaker is tripping.
Sensing arrangements depend on the installation
Some systems derive residual current from phase and neutral sensors; others use external arrangements. Trip interpretation depends on the number of poles, neutral system, sensor positions and earthing scheme. It is unsafe to copy a setting from another installation.
Do not defeat earth-fault protection
Changing or disabling protection to keep a feeder energized could leave a dangerous fault undetected. The approved protection coordination study, manufacturer manual and qualified protection engineer govern any change.
The event history preserves crucial evidence
Repeated closing can damage equipment and erase or complicate fault evidence. Record the exact event, connected feeders, load conditions and recent changes. Follow the site fault isolation and permit-to-work process.
Questions to narrow the problem
Collect existing operating records first. Inspection or electrical testing requires a qualified person and appropriate authorization.
- What is the ACB model and trip unit model?
- What exact fault code and time stamp appear in the trip record?
- Did the trip follow a new connection, maintenance or a feeder change?
- What does the approved SLD show for neutral and earth-fault sensors?
- Are relevant inspection and commissioning records available?
What to do next
Keep the breaker in the condition required by the site safety procedure. Arrange an authorized protection and installation review before resetting or investigating the circuit.
Common questions
Is an ACB earth-fault trip proof of a bad breaker?
No. A real circuit fault or an issue with the sensing system can cause an indication. Review the trip record and installation.
Can the ground-fault setting be disabled to restore supply?
This should not be done based on a web guide. Changes to protective functions require a formal engineering review and authorization.
Technical references
The linked sources explain general fault principles. The site-approved equipment manual and protection design take precedence.
- Schneider Electric: MicroLogic ground-fault protection
- Schneider Electric: MicroLogic 6 equipment ground-fault function
Record your electrical fault
Electrical Doctor helps organize symptoms and prepare preliminary case notes. It does not authorize repair or switching work.
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