An earth fault is insulation failure between a phase conductor and earth, a structure, or metalwork bonded to earth. It is the most common fault type on overhead lines and cables, around 70 to 80 percent of events. Its current depends heavily on the earthing method: very high on solidly earthed networks, limited to hundreds of amperes by resistance earthing, and only capacitive charging current on unearthed or compensated systems, which changes how it must be detected.
Sensitive earth fault picked up on feeder 9 at 40 A, the patrol found a gum tree leaning on the B phase.
North Americans say ground fault; most of the rest of the English-speaking world says earth fault.
Also heard as
- ground fault
- line-to-ground fault
- SLG fault
- E/F
Related terms
Earthing system
Arrangement describing how a supply's neutral and an installation's exposed metalwork are connected to earth.
RCD
Residual current device: trips when the current going out on the live conductors does not all come back.
Touch voltage
Voltage a person bridges between a hand on faulted metalwork and their feet or other hand during a fault.
Fault current
Abnormally high current that flows when insulation fails and a short circuit or earth fault forms.