51
Time overcurrent
An overcurrent function with a documented time characteristic.
Protection functions
Protection functions · 51G
Time ground-overcurrent protection
Supervises ground-current overcurrent with the timing defined by the selected relay and scheme.
SLD / Schematic · 51G
What it represents
Supervises ground-current overcurrent with the timing defined by the selected relay and scheme.
The drafting record should connect this function to the ground-current measurement input and grounding arrangement, then trace the timed earth-fault output and breaker trip path. Keep the complete designation and equipment tag together so that the SLD, relay logic and terminal schedule describe the same implementation.
The cited mapping is a public manufacturer example (SEL generator protection feature table). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme.
How to read it
- Identify the ground-current measurement input and grounding arrangement.
- Trace the timed earth-fault output and breaker trip path.
Information to show or reference
- Label the ground-current measurement input and grounding arrangement.
- Cross-reference the timed earth-fault output and breaker trip path.
- Retain the complete suffix, selected device tag and manufacturer manual revision.
A distinction that matters
Ground-current 51G and neutral-current 51N labels can reflect different inputs; do not merge them without the equipment documentation.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Generator protection feature and function comparison
Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original.
IEEE C37.2-2022: power-system device function numbers
Device-number and suffix convention. This page is not a reproduction of the full licensed standard.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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